Grade 11 / Study of sequences 66 exercises (including 58 corrected)

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2345678I-123JOCf ChingQuizz : 7 exercises available for Quizz assessment : 1. Variations of the first terms of arithmetic and geometric sequences E.6015 Definition: Let u n be a sequence defined for all n N . The sequence u n is said to be strictly increasing if for all n N , we have : u n +1 > u n the sequence u n is said to be strictly decreasing if for all n N , we have : u n +1 <u n the sequence u n is said to be constant if for all n N , we have : u n +1 = u n Consider the arithmetic sequence u n n N with first term 5 and common difference 2 . 1 Give the first four terms of the sequence u n . 2 Express the value of the term u n in terms of its rank n . 3 What conjecture can be made about the variation of the terms of the sequence u n ? E.6016 Consider the geometric sequence u n n N with first term 24 and reason 1 2 . 1 Give the first four terms of the sequence u n . 2 Give the expression of the general term of the sequence u n as a function of its rank n . 3 What conjecture can be made about the variation of the terms of the sequence u n ? E.6653 In each case, specify, if possible, the direction of variation of the sequences : 1 u n is an arithmetic sequence whose first term is posi-tive and whose reason is negative. 2 v n is a geometric sequence whose first term is negative and whose reason is strictly greater than 1. 3 w n is a geometric sequence whose first term is positive and reason is negative. 2. Variations of the first terms of an explicitly defined sequence E.5089 Consider the function f defined on R + whose representative curve C f is given in the orthonormal frame O ; I ; J below : We define the sequence u n by the relation: u n = f ( n ) for any integer n N . 1 Justify that the term u 4 has the value 3 2 . 2 a Determine the value of terms : u 0 ; u 1 ; u 2 ; u 3 ; u 4 ; u 5 ; u 6 b Say whether the statements below are true or not : ˇ The terms of the sequence u n for i 0 ; 1 ; 2 are ordered in descending order. ı ˇ The terms of the sequence u n for i 3 ; 4 ; 5 are ordered in ascending order. ı E.1585 Consider the two sequences u n and v n defined for any natural number n ( n N ) : u n = 2 · n 2 n + 1 ; v n = 4 n 1 + n 1 Determine the first 5 terms of these two sequences. 2 Conjecture the direction of variations of the sequence u n and v n . E.8477 Consider the two sequences u n and v n defined for any natural number n ( n N ) by: u n = n 3 3 · n 2 + 2 · n + 2 ; v n = 3 · 1 + ( 1) n + 2 1 Determine the first 5 terms of the sequences u n and v n 2 For each of the conjectures, say whether they are proba-ble or not : ˇ the sequence u n is constant. ı ˇ the following v n is constant. ı 3. Variations of the first terms of a sequence defined by recurrence https://chingmath.fr chapExoCorrec/6015 sacados/6015 chapExoCorrec/6016 sacados/6016 chapExoCorrec/6653 sacados/6653 chapExoCorrec/5089 sacados/5089 2345678I-123JOCf chapExoCorrec/1585 sacados/1585 chapExoCorrec/8477 sacados/8477
-2-1234I-12JOCf -4-3-2-1234I-3-2-123JOCf E.2378 Consider the function f defined on [ 2 ; 4] whose representative curve C f is given below : Consider the sequence u n n N defined by the relation u 0 = 3 ; u n +1 = f u n for all n N 1 Complete the following table with the first terms of the sequence u n : n 0 1 2 3 4 5 6 7 8 9 u n 2 For each of the statements below, state whether they are true or false : ˇ the sequence u n is strictly decreasing on N . ı ˇ the sequence u n is constant from rank 3 . ı E.8478 1 Consider the sequence u n defined for any natural num-ber n ( n N ) by: u 0 =2 ; u n +1 = 1 2 · u n 1 4 a Determine the 4 first terms of the suite u n . b Conjecture the variation of the sequence u n 2 Consider the sequence v n defined for any natural num-ber n ( n N ) by: v 0 = 1 ; v n +1 = 1 2 · v n 1 4 a Justify comparisons : v 0 <v 1 <v 2 <v 3 b Conjecture the variation of the sequence v n E.8479 Consider the sequence u n defined for any natural number n ( n N ) by: u 0 = 1 ; u n +1 = 2 1 + 2 u n 1 Determine the first 5 terms of the suite u n . 2 Conjecture the direction of variations of the sequence u n . 3 Conjecture the explicit expression of the general term of the sequence u n as a function of its rank n . 4. Variations: constant or periodic sequences E.2978 In the plane provided with an or-thonormal reference frame O ; I ; J , consider the representa-tion C f of a function f defined on the interval [ 4 ; 4] : 1 Consider the sequence ( u n ) defined for any natural num-ber n ( n N ) defined by: u 0 = 4 ; u n +1 = f u n a Determine the value of the first 6 terms of the suite u n . b Determine the value of term u 100 . 2 Consider the sequence ( v n ) defined for any natural num-ber n ( n N ) defined by: v 0 = 2 ; v n +1 = f v n Determine the value of the term v 100 . E.2953 Consider the sequence u n n N de-fined by the following recurrence relation: u 0 = 3 ; u n +1 = 1 u n 1 + u n for all n N 1 Determine the first five terms of the sequence u n . 2 Show that we have the following relationship : u n +2 = u n for all n N 3 What can be said about the terms of this sequence? 4 We admit that the term of rank n of the sequence u n admits an expression of the form : u n = a · 1 ( 1) n + b pour tout n N where a and b are two real numbers ( a;b R ) . Determine the values of a and b . 5. Variations: explicit sequences https://chingmath.fr chapExoCorrec/2378 sacados/2378 -2-1234I-12JOCf chapExoCorrec/8478 sacados/8478 chapExoCorrec/8479 sacados/8479 chapExoCorrec/2978 sacados/2978 -4-3-2-1234I-3-2-123JOCf chapExoCorrec/2953 sacados/2953
unest croissanteunest décroissanteu0>0etr>0u0>0etr<0u0<0etr>0u0<0etr<0 E.8485 The sequence u n n N is de-fined by: u n = 2 · n 2 3 · n + 2 for all n N Study the monotonicity of each of the sequences below, by studying the function f verifying the relation: u n = f ( n ) for all n N E.2386 Consider the sequence u n n N whose term of rank n is given by the formula : u n = n 2 7 · n + 1 1 Using the calculator, complete the table below : n 0 1 2 3 4 5 6 7 8 9 10 u n 2 After giving the table of variations of the function f whose image of x is defined by: f ( x ) = x 2 7 · x + 1 Establish that the sequence u n is increasing from rank 4. 6. Variations: explicit sequences with derivatives E.2382 The sequence u n is defined by: u n = 2 · n 2 +1 2 · n +5 for all n N Consider the function f defined by: f ( x ) = 2 · x 2 + 1 2 · x + 5 1 Give the defining set D f of the function f . 2 Establish that the function f derived from the function f admits as expression on D f : f ( x ) = 4 · x 2 + 20 · x 2 (2 · x + 5) 2 3 Draw up the table of variations of the function f . 4 Justify that the sequence u n is increasing from rank 1 . 5 Can we say that the sequence u n is increasing on N ? E.2410 Establish the monotonicity on N of the sequence u n n N defined by the explicit formula : u n = n 2 1 n for all n N . 7. Variations of arithmetic sequences E.10424 Consider the suite u n arithmetic, defined for any n N , with first term of 2 and reason 3 : 1 Give the expression of the terms of the sequence u n as a function of their rank n . 2 For n N , simplify the expression u n +1 u n 3 Deduce the direction of variation of the sequence u n . Proposition: let u n be an arithmetic sequence : u n is strictly decreasing if, and only if, its reason is strictly negative ; u n is strictly increasing if, and only if, its reason is strictly positive ; u n is constant if, and only if, its reason is zero; E.10425 Let u n be an arithmetic sequence with first term u 0 and reason r . 1 Connect the corresponding assertions : 2 A quelle (s) condition (s) arithmetic sequence is constant? E.8495 Let u n n N be the arithmetic se-quence of first term 1 and reason 3 . Justify that the sequence u n is an increasing sequence on N . E.10423 Let v n n N be the sequence defined for any natural number n ( n N ) and whose term of rank n admits the expression : v n = 4 n Justify that the sequence v n is decreasing on N . E.2380 Let u n n N be the sequence whose rank term n is defined by: u n = 32 n + 102 for all n N Show that this sequence is decreasing. https://chingmath.fr chapExoCorrec/8485 sacados/8485 fichierPlus/8485/diapoCorrection.pdf chapExoCorrec/2386 sacados/2386 chapExoCorrec/2382 sacados/2382 fichierPlus/2382/ chapExoCorrec/2410 sacados/2410 sacados/10424 sacados/10425 unest croissanteunest décroissanteu0>0etr>0u0>0etr<0u0<0etr>0u0<0etr<0 chapExoCorrec/8495 sacados/8495 chapExoCorrec/10423 sacados/10423 chapExoCorrec/2380 sacados/2380
0<q<1qq>1u0<0u0u0>0 unest croissanteunest décroissanteu0>0etq>1u0>0et0<q<1u0>0et1<q<0u0>0etq<1u0<0etq>1u0<0et0<q<1u0<0et1<q<0u0<0etq<1 8. Variations of geometric sequences E.10427 Consider the sequence u n defined for all n N geometric terms with first term 3 and common ratio 0.1 . 1 Express the term of the sequence u n of rank n in terms of n . 2 Simplify and factor the expression u n +1 u n . 3 Deduce the direction of variation of the sequence u n . Proposition: Let u n be a geometric sequence with com-mon ratio q . If u 0 > 0 and q> 1 , then the sequence u n is strictly increasing. If q =1 , then the sequence u n is constant. If u 0 > 0 and 0 <q< 1 , then the sequence u n is strictly decreasing. E.9846 Consider the suite u n n N geomet-ric with first term u 0 and reason q . In the table below, indicate the direction of variation of the sequence u n as a function of the value of its characteristic elements : E.10426 Let u n be a geometric sequence with first term u 0 and reason r . 1 Connect the corresponding assertions : 2 A quelle (s) condition (s) geometric sequence is constant? 9. Variations: difference between consecutive terms E.8480 Consider the sequence u n defined by: u n = 1 n 1 + n for all n N 1 Determine a simplified expression for u n +1 u n . 2 Deduce the variations of the sequence u n on N . E.8482 Consider the sequence u n defined by the relation: u n = n 3 4 · n 2 + n 3 for all n N 1 Establish the identity below for any natural number n : u n +1 u n = 3 · n 2 5 · n 2 . 2 Deduce that the sequence u n is increasing from rank 2 . E.8481 Let u n n N be defined by the ex-plicit relation: u n = n 3 2 n 2 3 n 1 Give the simplified expression of : u n +1 u n . 2 Deduce that the sequence ( u n ) is increasing for n greater than 2. E.3401 Consider the sequence u n defined by: u n = n 2 + 10 2 · n for any n N Justify that u n is increasing from rank 3 . E.6040 Consider the sequence u n defined on N defined by: u n = 5 n 1 ( n + 1) 2 1 Give the simplified and factorized form of the difference : u n +1 u n 2 Justify that the sequence u n is decreasing from rank 1 . https://chingmath.fr sacados/10427 chapExoCorrec/9846 sacados/9846 0<q<1qq>1u0<0u0u0>0 sacados/10426 unest croissanteunest décroissanteu0>0etq>1u0>0et0<q<1u0>0et1<q<0u0>0etq<1u0<0etq>1u0<0et0<q<1u0<0et1<q<0u0<0etq<1 chapExoCorrec/8480 sacados/8480 chapExoCorrec/8482 sacados/8482 chapExoCorrec/8481 sacados/8481 chapExoCorrec/3401 sacados/3401 chapExoCorrec/6040 sacados/6040
E.8496 Let u n be the sequence whose rank term n is defined by: u n = 2 n 1 for all n N 1 Establish the identity below for any strictly positive nat-ural number n ( n N ) : u n +1 u n = 2 2 n + 1 + 2 n 1 2 deduce that the suite u n is strictly increasing on N . E.8497 Let w n be the sequence whose rank term n is defined by: w n = 2 n 25 n for all n N Show that the sequence w n is increasing. E.8483 The sequence u n is defined by the explicit formula : u n = 5 + n n for all n N Determine the direction of variation of the sequence u n . 10. Variations: difference of consecutive terms (sequences defined by recurrence) E.5367 Let u n n N be the sequence defined by: u 0 = 1 ; u n +1 = u n u n 2 1 for all n N 1 Complete the table below of the first terms of the se-quence u n : n 0 1 2 3 4 u n 2 By studying the difference of two consecutive terms, show that the sequence u n is decreasing. E.10639 Consider the sequence u n defined on N by: u 0 = 3 ; u n +1 = u n 3 n + 7 1 Determine the first four terms of the sequence u n . 2 Determine from which rank the sequence u n is decreas-ing. 11. Variations: quotient of consecutive terms E.8494 1 Let u n be the geometric sequence defined at N with first term 2 and reason 4 . Justify that the sequence u n is increasing. 2 Let v n be the sequence defined for any natural number n ( n N ) and whose term of rank n admits the expres-sion : v n = 3 × 0 ; 2 n Justify that the sequence v n is decreasing. E.2381 Consider the sequence u n defined by: u n = 3 n 4 for any n N . Show that u n is strictly increasing. E.2522 Consider the sequence u n defined for any natural number n ( n N ) by: u n = 5 n n + 2 Show that the sequence u n n N is an increasing sequence on N . E.5491 Consider the sequence u n defined by: u n = 3 n 2 n + 1 for all n N Determine the variations of the sequence u n on N . E.10471 Consider the sequence u n defined on N by: u n = 2 n n 2 + 1 Determine from which rank the sequence u n is increasing. E.2451 The sequence u n is defined by the explicit formula : u n = 2 n 3 · n for all n N Determine the direction of variation of the sequence u n . 12. Variations from one rank: quotient of consecutive terms E.2450 Consider the sequence u n defined by the explicit formula : u n = 1.2 n n for any n N . 1 Give the simplified expression of u n +1 u n . https://chingmath.fr chapExoCorrec/8496 sacados/8496 chapExoCorrec/8497 sacados/8497 chapExoCorrec/8483 sacados/8483 chapExoCorrec/5367 sacados/5367 sacados/10639 chapExoCorrec/8494 sacados/8494 chapExoCorrec/2381 sacados/2381 chapExoCorrec/2522 sacados/2522 chapExoCorrec/5491 sacados/5491 sacados/10471 chapExoCorrec/2451 sacados/2451 chapExoCorrec/2450 sacados/2450
2 Show that u n is increasing from rank 5 . E.2670 Determine the direction of variation of the sequence u n defined by the relation: u n = n × (0.4) n for all n N E.8490 We record the sequence u n n N defined by the explicit formula : u n = 1.2 n n 2 for all n N . 1 Establish the following identity for any n N : u n +1 u n 1 = n 2 10 · n 5 5 · ( n + 1) 2 2 Deduce that the sequence u n is increasing from rank 11 . E.8489 The sequence u n n N is defined by: u n = n 2 n +1 for all n N Show that u n is strictly decreasing from rank 2 . 13. Link between recurring formula and explicit formula E.2383 1 Consider the sequence u n n N whose rank term n is de-fined by the recurrence relation: u 0 = 2 ; u n +1 = 1 3 · u n + 1 for any n N Calculate the first 4 terms of the sequence u n . 2 Consider the sequence v n n N defined explicitly by: v n = 1 2 · 1 3 n + 3 2 a Calculate the first 4 terms of the sequence v n b Establish that for any natural number n , we have : v n +1 1 3 · v n = 1 3 Deduce the equality of the sequences u n and v n . E.2384 1 Let u n n N , the sequence defined by the recurrence re-lation and the initial condition : u 1 = 1 ; u n +1 = 1 1 + 1 u n for any n N Calculate the first 4 terms of the sequence. 2 Let v n n N be the sequence whose term of rank n has the value : v n = 1 n for all n N a Give the value of v 1 . b Establish the following identity for any n N : 1 + 1 v n = n + 1 c Deduce that the sequence v n follows the recurrence relation below for any non-zero natural number: v n +1 = 1 1+ 1 v n 3 What can you say about the sequences u n and v n ? E.5136 Consider the two sequences u n and v n defined on N by: u 0 = 0 ; u n +1 = 3 · u n 2 · n + 3 for all n N v n = 3 n + n 1 1 a Establish that the two suites u n and v n have the same first term. b Show that the terms of the sequence v n verify the recurrence relation: v n +1 = 3 · v n 2 · n + 3 2 Justify the equality of the two sequences u n and v n . E.2385 1 The sequence u n n N is defined by the following recur-rence relation: u 0 = 2 ; u n +1 = 2 · u n 3 · n + 2 for all n N a By studying the previous recurrence relation, show that u 1 =6 . b Determine the value of the terms u 2 and u 3 . 2 The terms of the sequence v n n N are defined by the relation: v n = 2 n + 3 n + 1 for all n N a Give the first 4 terms of the sequence v n . b For any natural number n ( n N ) , establish the equal-ity: 2 · v n 3 · n + 2 = 2 n +1 + 3 · n +1 + 1 3 Deduce the equality of the sequences u n and v n . 14. Notions of limits: explicitly defined sequences E.8502 Consider the sequence u n whose terms are defined for any natural number n by the relation: u n = 10 · n 1 5 · n +1 1 a Using the calculator, complete the table of values below with values rounded to the nearest hundredth : n 0 1 2 3 4 5 u n b In the reference frame below and for n , place the se- https://chingmath.fr chapExoCorrec/2670 sacados/2670 chapExoCorrec/8490 sacados/8490 chapExoCorrec/8489 sacados/8489 chapExoCorrec/2383 sacados/2383 chapExoCorrec/2384 sacados/2384 chapExoCorrec/5136 sacados/5136 chapExoCorrec/2385 sacados/2385 chapExoCorrec/8502 sacados/8502
23456I-12JO quence of points A n whose coordinates are defined by: A n ( n ; u n ) 2 a Using the calculator, observe the representative curve C f in an orthonormal frame of reference of the function f defined by: f ( x ) = 10 · x 1 5 · x + 1 b What conjecture can be made about the limit of the sequence u n when n tends to + ? E.8504 Using the calculator, conjecture the limit of each of the sequences defined below when n tends to + : the sequence u n defined for any natural number n ( n N ) by: u n = 4 · n 1+12 · n the sequence v n defined for any natural number n ( n N ) by: v n = n 2 +2 · n 3 the sequence w n defined for any natural number n ( n N ) by: w n = ( 1) n n +1 E.8503 1 Let u n be an arithmetic sequence with first term u 0 and reason r . Complete the double-entry table below, indicating the value of lim n ↦→ + u n in each case r> 0 r< 0 u 0 > 0 u 0 < 0 2 Let v n be a geometric sequence with first term u 0 and reason q . Complete the double-entry table below, indi-cating, in each case if possible, the value of lim n ↦→ + v n v 0 > 0 v 0 < 0 q> 1 0 <q< 1 1 <q< 0 q< 1 15. Notions of limits: sum of the terms of a sequence E.6029 Consider the sequence u n geomet-ric of first term 5 and reason 2 3 . Let S n be the sum of the ( n +1) first terms of the sequence u n : S n = u 0 + u 1 + · · · + u n 1 + u n 1 Justify that the sequence S n is increasing. 2 Give the expression of the term S n as a function of n . 3 a Using a calculator, complete the table below, round-ing values to the nearest thousandth : n 0 1 2 10 20 24 S n b What conjecture can be made about the limit of the sequence S n when n tends to + ? E.6013 A runner sets himself a challenge : he wants to circumnavigate Europe. On the first day, he covers 50 km . Through fatigue, from day to day, his daily distance travelled is reduced by 1 % . We note u n the length covered by the runner on the n -th day. Assuming that the runner continues his run indefinitely, we obtain a sequence u n defined for any non-zero natural number. 1 Determine the value of the first four terms of the se-quence u n . 2 a What is the nature of the sequence u n ? Give the characteristic elements of the sequence u n . b Express the term u n as a function of rank n . c What distance will the runner cover on 100 e day? We’ll round the value to the tenth of a kilometer. 3 For any natural number n , let S n be the sum of the first n terms of the sequence u n : S n = u 1 + u 2 + · · · + u n a Express the sum S n as a function of rank n . b Complete the following table, rounding values to the nearest tenth of a kilometer: https://chingmath.fr 23456I-12JO chapExoCorrec/8504 sacados/8504 chapExoCorrec/8503 sacados/8503 chapExoCorrec/6029 sacados/6029 chapExoCorrec/6013 sacados/6013
ABEtape no0ABEtape no1ABEtape no2ABEtape no3ABEtape no4ABEtape no5 Première ∏gure5cm:::Seconde ∏gure3cm n 10 100 500 750 1000 u n c What conjecture can be made about the limit of the terms of the sequence S n when n tends to + ? E.6014 The Heige Von Koch flake is con-structed as follows : We start from a segment [ AB ] of length 9 cm . To move from one step to the next, we cut each segment of the figure into three equal parts and replace the central ˇı segment with an equilateral triangle. Here’s a representation of the first 6 steps of this construc-tion : At each n step, we note u n the length of the ˇ line brisée ı thus obtained. We thus construct a sequence of numbers u n defined for any natural number n . 1 Determine the measure of the first three terms of the sequence u n . 2 a In step n , express the number of segments s n form-ing the ˇ line brisée ı as a function of n . b In step n , express the length n of each of the segments forming the ˇ line brisée ı as a function of n . 3 We note L n the length of the ˇ line brisée ı at step n . This gives a sequence L n of numerical terms defined for any natural number n . a Express the terms of the sequence L n in terms of their rank n . b Complete the table below, rounding values to the near-est hundredth of a centimeter: n 0 1 10 20 30 L n E.6039 In this exercise, any trace of research, however incomplete, or initiative, however unsuccessful, will be taken into account in the assessment. The quality of the justifications will also be taken into account. Consider the two figures below : The first figure is a square whose sides measure 5 cm ; The second figure is composed of a square whose sides measure 3 cm , to complete the figure, we add a new square whose dimensions have been reduced by the co-efficient 4 5 . We repeat this figure a number of times, but we don’t know how many times! Which of these two figures has the larger area? 16. Further study: arithmetic-geometric sequences and variation E.9844 Consider the sequence u n defined by the relation: u 0 = 2 ; u n +1 = 2 · u n + 0.5 for any n N 1 We define the sequence v n defined by the relation: v n = u n + 0.5 for all n N a Establish, for any n N , the equality: v n +1 = 2 · v n b Give the nature and characteristic elements of the straight line v n . c Give the direction of variation of the sequence v on N . Justify your answer. 2 a For any n N , set : u n +1 u n = v n +1 v n b Deduce the direction of variations of the sequence u n on N . E.9845 Consider the sequence u n ) defined on N by: u 1 = 0 ; u n +1 = 0.2 · u n + 0.04 for any n N 1 We define the sequence v n on N by the relation: v n = u n 0.05 a Establish equality for any n N : v n +1 = 0.2 · v n b Determine the nature and characteristic elements of the sequence v n . 2 a Establish equality for any n N : u n +1 u n = v n +1 v n b Deduce the direction of variation of the sequence u n E.6668 Consider the sequence u n defined by: u 0 = 2 ; u n +1 = 1 + 2 · u n 6 for all n N and the sequence v n , defined for any n N , by: v n = u n 3 1 Establish that the sequence v n is a geometric sequence whose characteristic elements and direction of variations will be given. 2 a For any n N , establish equality: u n +1 u n = v n +1 v n b Determine the direction of variation of the sequence u n . https://chingmath.fr chapExoCorrec/6014 sacados/6014 ABEtape no0ABEtape no1ABEtape no2ABEtape no3ABEtape no4ABEtape no5 chapExoCorrec/6039 sacados/6039 Première ∏gure5cm:::Seconde ∏gure3cm chapExoCorrec/9844 sacados/9844 chapExoCorrec/9845 sacados/9845 chapExoCorrec/6668 sacados/6668
17. Further study: arithmetic-geometric sequences and explicit formulas E.9843 Consider the sequence u n defined by the relation: u 0 = 8 ; u n +1 = 0.95 · u n + 0.5 for any n N 1 We define the sequence v n defined by the relation: v n = u n 10 for all n N a Justify that the sequence v n is a geometric sequence of reason 0.95 . Specify the value of its first term. b Express the terms of the sequence v n as a function of n . 2 Deduce an expression for the sequence u n as a function of n 3 Determine the limit of the terms of the sequence u n when n tends to + . E.9842 We wish to study the sequence ( u n ) of first term u 0 =5 defined by the following recurrence rela-tion : u n +1 = 1 3 u n + 4 for all n N We define the sequence v n by: v n = u n 6 for all n N 1 a Show that the sequence ( v n ) is a geometric sequence whose first term and reason will be specified. b Express v n as a function of rank n . 2 a Deduce the expression of u n as a function of n . b For any n N , establish that : u n +1 u n = 2 3 · 1 3 n c Deduce the direction of variations of the sequence u n . E.5368 Consider the sequence u n defined by: u 0 = 3 ; u n +1 = 3 4 · u n + 1 2 for any integer n N 1 Consider the sequence v n defined by the following re-lation for any natural number n : v n = 1 2 · u n 1 a Establish the equality below for any natural number n : v n +1 = 3 4 · v n b Give the direction of variation of the sequence v n . 2 Deduce the direction of variation of the sequence u n . 18. More: other uses for auxiliary suites E.8487 Consider the sequence v n defined by: v 0 = 1 ; v n +1 = v n + 2 · n + 3 for all n N 1 Determine the first five terms of the sequence v n . 2 What conjecture can be made about the terms of the sequence v n ? We define the sequence w n defined by: w n = v n +1 v n for any n N 1 Justify that the sequence w n is an arithmetic sequence. Specify the characteristic elements of this sequence. 2 Determine the expression of the sum S of the first n terms of the sequence w n . 3 Noting the equality n 1 k =0 w k + v 0 = v n , deduce the expres-sion of the term v n as a function of n . 4 Confirm the conjecture made in question b . 19. Further development: jointly defined suites E.8498 Consider the two sequences u n and v n defined for any natural number n by the relations : u 0 = 3 v 0 = 1 ; u n +1 = 2 · u n + v n 2 v n +1 = u n + 3 · v n 3 1 Determine the first three terms of the sequences u n and v n . 2 Admit that the terms of the sequences u n and v n are strictly positive numbers. Show that the sequences u n and v n are increasing on N . E.4235 Consider the sequences u n and v n defined by: u 0 = 0 ; u n +1 = u n + v n 2 for all n N v 0 = 12 ; v n +1 = u n + 2 · v n 3 for any n N 1 Demonstrate that the sequence w n defined by w n = v n u n is a convergent geometric sequence and that all its terms are positive. 2 Show that the sequence u n is increasing and then that the sequence v n is decreasing. https://chingmath.fr chapExoCorrec/9843 sacados/9843 chapExoCorrec/9842 sacados/9842 chapExoCorrec/5368 sacados/5368 chapExoCorrec/8487 sacados/8487 chapExoCorrec/8498 sacados/8498 chapExoCorrec/4235 sacados/4235
Motif0Motif1Motif2Motif3 Motif0Motif1Motif2Motif3 20. Unclassified financial years E.5973 1 a Consider the sequence u n defined by the relation: u 0 = 0 ; u n +1 = 1 2 u n for all n N Determine the first four terms of the sequence u n . b Consider the sequence v n defined by the relation: v n = n n + 1 for any n N . Determine the first four terms of the sequence v n . c What conjecture can be made about the sequences u n and v n ? 2 a Simplify the following expression : v n +1 · 2 v n b Justify that the two suites u n and v n are equal. E.10569 Consider the step-by-step pattern con-struction whose first five steps are shown below : 1 How many tiles are needed to construct pattern 4? pat-tern 5? 2 We note u n the number of tiles required to construct pattern n . a Give the recurrence formula verified by the sequence u n . b Establish that the terms of the sequence u n admit the explicit formula : u n = 2 n 2 + 5 n + 4 E.10570 Consider the step-by-step pattern con-struction whose first five steps are shown below : 1 How many tiles are needed to construct pattern 4? pat-tern 5? 2 We note u n the number of tiles needed to construct pat-tern n . a Give the recurrence formula verified by the sequence u n . b Establish that the terms of the sequence u n verify the explicit formula : u n = 1 3 · n 3 + 3 2 · n 2 + 13 6 · n + 1 https://chingmath.fr chapExoCorrec/5973 sacados/5973 sacados/10569 Motif0Motif1Motif2Motif3 sacados/10570 Motif0Motif1Motif2Motif3