Grade 12 / Annals on sequences 22 exercises (including 21 corrected)

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12345678ABCn01234u2492463v7142856 Fonctionf(n)u0Pouriallantde1ànu·FinpourRenvoyeruFonctionf(n)u0Pouriallantde0àn1u·FinpourRenvoyeruAlgorithme1Algorithme2 012345678910111220406080100120140160001226312420530642756872990101101113212156 1. Suite studies E.6762 Let u be the sequence defined by u 0 =2 and, for any natural number n , by: u n +1 = 2 · u n + 2 · n 2 n Consider also the sequence v defined, for any natural number n , by: v n = u n + 2 · n 2 + 3 · n + 5 1 Here is an extract from a spreadsheet : What formulas have been written in the cells C2 and B3 and copied down to display the terms of the sequences u and v ? 2 Determine, with justification, an expression for v n and u n as a function of n only. E.6256 Consider the sequence u n de-fined by: u 0 = 0 ; u n +1 = u n + 2 · n + 2 for any n N 1 Calculate u 1 and u 2 . 2 Consider the two functions below, taken from algorithms, taking as argument an integer n : Which of these two functions returns the value of the term u n of rank n , the value supplied as an argument when the function is called? 3 Using the algorithm, we obtained the table and scatter-plot below n figure on the x-axis and u n on the y-axis. a What conjecture can be made about the direction of variation of the sequence u n ? Demonstrate this conjecture. b The parabolic shape of the point cloud leads us to conjecture the existence of three real numbers a , b and c such that, for any natural number n : u n = a · n 2 + b · n + c . In the context of this conjecture, find the values of a , b and c using the information provided. 4 For any natural number n , the sequence v n is defined by: v n = u n +1 u n a Express v n in terms of the natural number n . What is the nature of the sequence v n ? b We define, for any natural number n : S n = n k =0 v k = v 0 + v 1 + · · · + v n Show that, for any natural number n : S n = ( n + 1)( n + 2) c Demonstrate that, for any natural number n : S n = u n +1 u 0 , then express u n as a function of n . https://chingmath.fr chapExoCorrec/6762 sacados/6762 12345678ABCn01234u2492463v7142856 chapExoCorrec/6256 sacados/6256 Fonctionf(n)u0Pouriallantde1ànu·FinpourRenvoyeruFonctionf(n)u0Pouriallantde0àn1u·FinpourRenvoyeruAlgorithme1Algorithme2 012345678910111220406080100120140160001226312420530642756872990101101113212156
E.5079 Part A Consider the function f , taken from an algorithm, and whose argument is a natural number. Function f(N) U 0 For k ranging from 0 to N 1 U 3 · U 2 · k+3 End To Return U What is the value returned by this function when called with the value 3 for the argument N ? Part B y Consider the sequence u n defined by u 0 =0 and, for any integer nature n : u n +1 = 3 · u n 2 · n + 3 1 Calculate u 1 and u 2 . 2 a Demonstrate by recurrence that, for any natural number n : u n n b Deduce the limit of the sequence u n . 3 Demonstrate that the sequence u n is increasing. 4 Let the sequence v n be defined, for any natural number n , by v n = u n n + 1 a Demonstrate that the sequence v n is a geometric se-quence. b Deduce that, for any natural number n : u n = 3 n + n 1 5 Let p be a non-zero natural number. a Why can we say that there exists at least one integer n 0 such that, for any n n 0 , u n 10 p ? We are now interested in the smallest integer n 0 . b Justify that : n 0 3 · p . c Using the calculator, determine this integer n 0 for the value p =3 . d Propose a function which, for a value p passed as an argument, returns the value of the smallest integer n 0 such that, for any n n 0 , we have u n 10 p . E.5019 1 Consider the function f , given below and derived from an algorithm, taking the arguments a , b , N of non-zero integer values : Function f(a,b,N) u a v b n 0 As long as n<N n n+1 u a + b 2 v a 2 + b 2 2 a u b v . End As long as Renvoyer ( u ; v) Reproduce and complete the following table, showing the values taken by the function variables f during step-by-step execution and when the the call is made with the values a =4 , b =9 and N =2 . Successive values of u and v will be rounded to the thousandth. n a b u v 0 4 9 1 2 In the following, a and b are two real numbers such that 0 <a<b . Consider the sequences u n and v n defined by: u 0 = a , v 0 = b and, for any natural number n : u n +1 = u n + v n 2 ; v n +1 = u 2 n + v 2 n 2 2 a Demonstrate by recurrence that, for any natural number n , we have : u n > 0 ; v n > 0 b Demonstrate that, for any natural number n : v 2 n +1 u 2 n +1 = u n v n 2 2 Deduce that, for any natural number n , we have : u n v n . 3 a Demonstrate that the sequence u n is increasing. b Compare v 2 n +1 and v 2 n . Deduce the direction of varia-tion of the sequence v n . https://chingmath.fr chapExoCorrec/5079 sacados/5079 Polynesie 2012 5 points chapExoCorrec/5019 sacados/5019 Asie Juin 2012 5 points
-3-2-123456I-1234567JOCf E.3836 Consider the sequence of real num-bers u n defined on N by: u 0 = 1 u 1 = 1 2 u n +2 = u n +1 1 4 · u n for any natural number n . 1 Calculate u 2 and deduce that the sequence u n is nei-ther arithmetic nor geometric. 2 We define the sequence v n by posing, for any natural number n : v n = u n +1 1 2 · u n a Calculate v 0 . b Express v n +1 as a function of v n . c Deduce that v n is geometric of reason 1 2 . d Express v n in terms of n . 3 We define the sequence w n by posing, for any natural number n : w n = u n v n a Calculate w 0 . b Using the equality u n +1 = v n + 1 2 · u n , express w n +1 as a function of u n and v n . c Deduce that for any n of N : w n +1 = w n +2 . d Express w n as a function of n . 4 Show that for any natural number n : u n = 2 · n 1 2 n 5 For any natural number n , we pose : S n = k = n k =0 u k = u 0 + u 1 + · · · + u n Demonstrate by recurrence that for any n N : S n = 2 2 n + 3 2 n E.3210 The sequence u n is defined by: u 0 = 1 ; u n +1 = 1 2 u n + n 1 for all n N 1 a Show that for any n 3 : u n 0 . b Deduce that for any n 4 : u n n 2 . c Deduce the limit of the sequence ( u n ) . 2 We define the sequence ( v n ) by: v n = 4 u n 8 n + 24 a Show that ( v n ) is a decreasing geometric sequence whose reason and first term will be given. b Show that for any natural number n : u n = 7 · 1 2 n + 2 n 6 . c Verify that for any natural number n , u n = x n + y n ( x n ) is a geometric sequence and ( y n ) an arithmetic se-quence whose first term and reason are to be specified for each. d Deduce the expression of S n = n k =0 u k as a function of n . E.3472 Consider the sequence u n n N defined by: u 0 = 1 u n +1 = 1 3 · u n + n 2 for any natural number n . 1 Calculate u 1 , u 2 and u 3 . 2 a Demonstrate that for any natural integer n 4 : u n 0 . b Deduce that for any natural number n 5 : u n n 3 c Deduce the limit of the sequence u n n N 3 We define the sequence v n n N by: For any n N : v n = 2 · u n + 3 · n 21 2 . a Show that the sequence v n n N is a geometric se-quence whose reason and first term will be given. b Deduce that : for any n N : u n = 25 4 · 1 3 n + 3 2 · n 21 4 . c Let the sum S n be defined for any natural integer n by: S n = n k =0 u k Determine the expression of S n as a function of n . 2. Suites, variations and limits E.3415 Consider the function f defined on −∞ ; 6 by: f ( x ) = 9 6 x We define the sequence U n by: U 0 = 3 ; U n +1 = f U n for any n N 1 The representative curve of the function f is given be-low accompanied by that of the straight line of equation y = x . https://chingmath.fr chapExoCorrec/3836 sacados/3836 Antilles-Guyanne Septembre 2010 5 points chapExoCorrec/3210 sacados/3210 Antilles-Guyane Septembre 2005 5 points chapExoCorrec/3472 sacados/3472 chapExoCorrec/3415 sacados/3415 -3-2-123456I-1234567JOCf
Construct, in the above reference frame, the points : M 0 ( U 0 ; 0) ; M 1 ( U 1 ; 0) ; M 2 ( U 2 ; 0) ; M 3 ( U 3 ; 0) ; M 4 ( U 4 ; 0) What conjectures can be made regarding the direction of variation and possible convergence of the sequence U n ? 2 a Demonstrate that si x< 3 then 9 6 x < 3 . Deduce that U n < 3 for any natural number n . b Study the direction of variation of the sequence U n . c What can be deduced from questions 2 a and 2 b ? 3 Consider the sequence V n defined by V n = 1 U n 3 for any natural number n . a Demonstrate that the sequence V n is an arithmetic sequence of reason 1 3 . b Determine V n then U n as a function of n . c Calculate the limit of the sequence U n . E.5864 Consider the sequence u n de-fined by u 0 = 1 2 and such that for any natural number n : u n +1 = 3 · u n 1 + 2 · u n 1 a Calculate u 1 and u 2 . b Demonstrate, by recurrence, that for any natural num-ber n : 0 <u n . 2 We admit that for any natural number n : u n < 1 . a Demonstrate that the sequence u n is increasing. b Demonstrate that the sequence u n converges. 3 Let v n be the sequence defined, for any natural number n by: v n = u n 1 u n a Show that the sequence v n is a geometric sequence of reason 3 . b Express for any natural number n , v n as a function of n . c Deduce that, for any natural number n : u n = 3 n 3 n + 1 d Determine the limit of the sequence u n . E.3474 Let f be the function defined on the interval 0 ; + by: f ( x ) = 6 5 x + 1 The aim of this exercise is to study sequences u n defined by a first positive or zero term u 0 and verifying for any natural number n : u n +1 = f ( u n ) 1 Study of function properties f : a Study the direction of variation of the function f on the interval 0 ; + . b Solve in the interval 0 ; + the equation : f ( x ) = x . Note ¸ the solution. c Show that if x belongs to the interval 0 ; ¸ , then f ( x ) belongs to the interval 0 ; ¸ . Similarly, show that if x belongs to the interval ¸ ; + , then f ( x ) belongs to the interval ¸ ; + . 2 Study the sequence u n for u 0 =0 : In this question, consider the sequence u n defined by u 0 =0 and for any natural number n : u n +1 = f u n = 6 5 u n + 1 a On the graph shown in Appendix 2, are represented the curves with equations y = x and y = f ( x ) . Place the point A 0 of coordinates ( u 0 ; 0) , and, using these curves, construct from A 0 the points A 1 , A 2 , A 3 and A 4 with ordinate zero and abscissa u 1 , u 2 , u 3 and u 4 respectively. What conjectures can be made about the direction of variation and convergence of the sequence u n ? b Demonstrate, by recurrence, that for any natural num-ber: 0 u n u n +1 ¸ . c Deduce that the sequence u n is convergent and de-termine its limit. 3 Study the sequences u n according to the values of the positive or zero real u 0 . In this question, any trace of argumentation, however incomplete, or initiative, however unsuccessful, will be taken into account in the assessment. What can be said about the direction of variation and convergence of the sequence u n depending on the val-ues of the positive or zero real u 0 ? https://chingmath.fr chapExoCorrec/5864 sacados/5864 chapExoCorrec/3474 sacados/3474
23456789I23456789JOC E.6269 Consider the numerical sequence u n defined on N by: u 0 = 2 ; u n +1 = 1 2 · u 2 n + 3 · u n 3 2 pour tout n N Part A : Conjecture 1 Calculate the exact values, given in irreducible fractions, of u 1 and u 2 . 2 Give an approximate value to the nearest 10 5 of the terms u 3 and u 4 . 3 Conjecture the direction of variation and convergence of the sequence u n . Part B: Validation of conjectures Consider the numerical sequence v n defined for any natural number n , by: v n = u n 3 1 Show that, for any natural number n : v n +1 = 1 2 · v 2 n . 2 Demonstrate by recurrence that, for any natural number n : 1 v n 0 . 3 a Demonstrate that, for any natural number n : v n +1 v n = v n · 1 2 · v n + 1 . b Deduce the direction of variation of the sequence v n . 4 Why can we then say that the sequence v n converges? 5 We note the limit of the sequence v n . We admit that belongs to the interval 1 ; 0 and ver-ifies the equality: = 1 2 · 2 . Determine the value of . 6 Are the conjectures made in part A validated? E.6763 Part A Let u n be the sequence defined by its first term u 0 and, for any natural number n , by the relation: u n +1 = a · u n + b ( a and b real non-zero such that a =1 ) We pose, for any natural number n : v n = u n b 1 a 1 Demonstrate that, the sequence v n is geometric of rea-son a . 2 Deduce that if a belongs to the interval 1 ; 1 , then the sequence u n has limit b 1 a . Part B In March 2015 , Max buys a green plant measuring 80 cm . He is advised to prune it every year, in March, by cutting off a quarter of its height. The plant will then grow by 30 cm over the following twelve months. As soon as he gets home, Max prunes his plant. 1 How tall will the plant be in March 2016 before Max prunes it? 2 For any natural number n , let h n be the height of the plant, before it is pruned, in March of the year (2015+ n ) . a Justify that, for any natural number n : h n +1 = 0.75 · h n + 30 b Use the calculator to conjecture the direction of varia-tion of the sequence h n . Demonstrate this conjecture (reasoning by recurrence may be used) . c Is the sequence h n convergent? Justify the answer. https://chingmath.fr 23456789I23456789JOC chapExoCorrec/6269 sacados/6269 chapExoCorrec/6763 sacados/6763
KWUV012 E.6962 The aim of this exercise is to study sequences of positive terms whose first term u 0 is strictly greater than 1 and possessing the following property: for any natural number n> 0 , the sum of the first n consecutive terms is equal to the product of the first n consecutive terms. We admit that such a sequence exists and note it u n . It therefore verifies three properties : u 0 > 1 for any n 0 , u n 0 for all n> 0 : u 0 + u 1 + ··· + u n 1 = u 0 × u 1 ×···× u n 1 1 We choose u 0 =3 . Determine u 1 and u 2 . 2 For any integer n> 0 , we note : s n = u 0 + u 1 + ··· + u n 1 = u 0 × u 1 ×···× u n 1 . In particular, we have s 1 = u 0 . a Verify that for any integer n> 0 : s n +1 = s n + u n and s n > 1 b Deduce that for any integer n> 0 : u n = s n s n 1 c Show that for any n 0 : u n > 1 . 3 The function f below is desiredbelow returns the value of one of the terms in the sequence u n the arguments u and n of the function are respectively the first term of the sequence u n and the rank of the desired term. Function f(u,n) s u For i from 1 to n u ... s ... End for Return u a Copy and complete the processing part of the above algorithm. b The table below gives values rounded to the thou-sandth of u n for different values of the integer n : n 0 5 10 20 30 40 u n 3 1.140 1.079 1.043 1.030 1.023 What conjecture can be made about the convergence of the sequence u n ? 4 a Justify that for any natural number n> 0 : s n >n . b Deduce the limit of the sequence s n and then that of the sequence u n . E.5854 Let two sequences u n and v n be defined by u 0 =2 and v 0 =10 and for any natural number n : u n +1 = 2 · u n + v n 3 ; v n +1 = u n + 3 · v n 4 Part A Consider the function f ex-tracted from an algorithm its argument n is an integer greater than or equal to 1 : We call the function f with the value n =2 as its argument. Copy and complete the table given be-low giving the state of the vari-ables during this call: Function f(n) K 0 U 2 V 10 As long as K<n K K+1 W U U 2 · U+V 3 V W + 3 · V 4 End as long as Renvoyer ( U ; V) Part B 1 a Show that for any natural number n : v n +1 u n +1 = 5 12 · v n u n b For any natural number n , we pose : w n = v n u n . Show that for any natural number n : w n = 8 · 5 12 n . 2 a Show that the sequence u n is increasing and that the sequence v n is decreasing. b Deduce from the results of questions 1 b and 2 a that for any natural number n , we have : u n 10 ; v n 2 c Deduce that the sequences u n and v n are conver-gent. 3 Show that the suites u n and v n have the same limit. 4 Show that the sequence t n defined by t n =3 · u n +4 · v n is constant. Deduce that the common limit of the sequences u n and v n is 46 7 https://chingmath.fr chapExoCorrec/6962 sacados/6962 chapExoCorrec/5854 sacados/5854 KWUV012
E.5077 The purpose of this exercise is to study the sequence u n defined by: u 0 = 3 ; u n +1 = 1 2 · u n + 7 u n pour tout n N We may use without demonstration the fact that for any nat-ural number n , u n > 0 . 1 We denote by f the focntion defined on the interval 0 ; + by: f ( x ) = 1 2 · x + 7 x ( ) Show that the function f admits a minimum. Deduce that for any natural number n : u n 7 2 a Let n be any natural number. Study the sign of u n +1 u n . b Why can we deduce that the sequence u n is conver-gent? c From the relation ( ) we deduce that the limit of this sequence is such that : = 1 2 · + 7 . Determine . 3 Demonstrate that for any natural number n : u n +1 7 = 1 2 · u n 7 2 u n 4 We define the sequence d n by: d 0 = 1 ; d n +1 = 1 2 · d n 2 pour tout n N a Demonstrate by recurrence that for any natural num-ber n : u n 7 d n b Here’s a function from an algorithm taking as argu-ment p which is a natural integer. Function f(p) d 1 n 0 As long as d>10 p d 0.5 · d 2 n n+1 End As long as Return n Calling the function with the value 9 , the value re-turned is the number 5 . What inequality can be deduced for d 5 ? ? Justify that u 5 is an approximate value of 7 to the nearest 10 9 . 3. Suites and logarithms E.5966 Part A Consider the sequence u n defined by: u 0 = 2 ; u n +1 = 1 + 3 u n 3 + u n for any natural number n All terms in this sequence are assumed to be definite and strictly positive. 1 Demonstrate by recurrence, that for any natural number n , we have : u n > 1 2 a Establish that, for any natural number n , we have : u n +1 u n = (1 u n )(1 + u n ) 3 + u n b Determine the direction of variation of the sequence u n . Deduce that the sequence u n converges. Part B Consider the sequence u n defined by: u 0 = 2 ; u n +1 = 1 + 0.5 u n 0.5 + u n for any natural number n . All terms in this sequence are assumed to be definite and strictly positive. 1 Consider the following algorithm: u 2 For i ranging from 1 to n u 1+0.5u 0.5+u End For Reproduce and complete the table below showing the val-ues taken by the variables i and u during the step-by-step execution of this algorithm. Values of u will be rounded to the thousandth. i 1 2 3 u 2 For n =12 , we extended the previous table and obtained : i 4 5 6 7 8 9 10 11 12 u 1.0083 0.9973 1.0009 0.9997 1.0001 0.99997 1.00001 0.999996 1.000001 Conjecture the behavior of the sequence u n at infinity. 3 Consider the sequence v n defined, for any natural num-ber n by: v n = u n 1 u n + 1 a Demonstrate that the sequence v n is geometric of reason 1 3 . b Calculate v 0 then write v n as a function of n . 4 a Show that, for any natural number n , we have : v n =1 . b Show that, for any natural number n , we have : u n = 1 + v n 1 v n c Determine the limit of the sequence u n . https://chingmath.fr chapExoCorrec/5077 sacados/5077 Metropole Septembre 2012 5 points chapExoCorrec/5966 sacados/5966
E.6264 A patient is given a drug by intra-venous injection. The quantity of drug in the blood decreases as a function of time. The aim of the exercise is to study, for different hypotheses, the evolution of this quantity minute by minute. 1 At time 0 an injection of 10 m‘ of drug is made. It is estimated that 20 % of the drug is eliminated per minute. For any natural number n , note u n the amount of drug, in m‘ , remaining in the blood after n minutes. Thus, u 0 =10 . a What is the nature of the sequence u n ? b For any natural number n , give the expression of u n as a function of n . c After how long does the amount of drug remaining in the blood become less than 1 % of the initial amount? Justify the answer. 2 At time 0 , a machine injects 10 m‘ of drug. It is esti-mated that 20 % of the drug is eliminated per minute. When the amount of drug falls below 5 m‘ , the machine re-injects 4 m‘ of product. After 15 minutes, the machine is stopped. For any natural number n , note v n the amount of drug, in m‘ , remaining in the blood at minute n . The following algorithm makes it possible, through the values taken by the variable v , to obtain the remaining quantity of drug minute by minute. v 10 For n ranging from 1 to 15 v 0.8 × V If v<5 Then v v+4 End If End For a Calculate the missing elements of the table below giv-ing, rounded to 10 2 and for n greater than or equal to 1 , the remaining minute-by-minute quantity of drug obtained with the algorithm. n 0 1 2 3 4 5 6 7 v n 10 8 6.4 8.15 n 8 9 10 11 12 13 14 15 v n 6.52 5.21 8.17 6.54 5.23 8.18 6.55 5.24 b After 15 minutes, what total amount of drug has been injected into the body? c We want to program the machine to inject 2 m‘ prod-uct when the amount of drug in the blood is less than or equal to 6 m‘ and that it stops after 30 minutes. Recopy the previous algorithm, modifying it so that, at the end of execution, the value of variable b is the quantity of drug, in m‘ , remaining in the blood minute by minute with this new protocol. 3 The machine is programmed so that : at time 0 , she injects 10 m‘ of medication, every minute, she injects 1 m‘ of medication. It is estimated that 20 % of the drug in the blood is elim-inated per minute. For any natural number n , note w n the amount of drug, in m‘ , present in the patient’s blood after n minutes. a Justify that for any natural number n : w n +1 = 0.8 · w n + 1 . b For any natural number n , we pose : z n = w n 5 . Show that z n is a geometric sequence whose reason and first term are to be specified. c Deduce the expression of w n as a function of n . d What is the limit of the sequence w n ? What inter-pretation can be given? E.3234 For any natural number n , we pose u n = n 10 2 n . This defines a sequence u n n N 1 Prove, for any non-zero natural number n , the following equivalence : u n +1 0.95 u n if, and only if, 1+ 1 n 10 1.9 2 Consider the function f defined on 1 ; + by: f ( x ) = 1 + 1 x 10 a Study the direction of variation and limit in + of the function f . b Show that there exists in the interval 1 ; + a single real number ¸ such that f ( ¸ )=1.9 . c Determine the natural number n 0 such that n 0 1 ¸ n 0 . d Show that, for any natural number n greater than or equal to 16 , we have : 1 + 1 n 10 1.9 . 3 a Determine the direction of variation of the sequence ( u n ) from rank 16 . b What can we deduce for the sequence? 4 Using reasoning by recurrence, prove, for any natural number n greater than or equal to 16, the framework: 0 u n 0.95 n 16 · u 16 Deduce the limit of the sequence u n n N E.3267 1 Let u be the sequence defined by: u 0 = 0 u n +1 = 1 2 u n for any natural number n . a Calculate u 1 , u 2 and u 3 . Each of these terms will be expressed as an irreducible fraction. b Compare the first four terms of the sequence u with the first four terms of the sequence w defined on N by: w n = n n + 1 . c Using reasoning by recurrence, show that, for any nat-ural number n : u n = w n . 2 Let v be the sequence with general term v n defined by: v n = ln n n + 1 ln denotes the neperian logarithm function : a Show that : v 1 + v 2 + v 3 = ln 4 b Let S n be the sum defined for any non-zero natural number n by: S n = v 1 + v 2 + · · · + v n Express S n as a function of n . Determine the limit of S n when n tends to + . https://chingmath.fr chapExoCorrec/6264 sacados/6264 chapExoCorrec/3234 sacados/3234 chapExoCorrec/3267 sacados/3267
4. Suites and integrations E.3161 Consider the sequences u n and v n defined, for any non-zero natural number n , by: u 1 = 1 u n = u n 1 + 1 n pour n 2 ; v n = u n ln n for n 1 1 a Calculate u 2 , u 3 and u 4 . b Show that, for any non-zero natural number n : u n = n k =1 1 k 2 a Show that, for any non-zero natural number k : 1 k + 1 k +1 k 1 x d x 1 k b Deduce that, for any integer n greater than or equal to 2 , we have the following inequalities: u n 1 ln n u n 1 n ; 0 v n 1 3 a Show that, for any non-zero natural number n : v n +1 v n = 1 n + 1 n +1 n 1 x d x b Deduce the direction of variations of the sequence ( v n ) . 4 Show that the sequence ( v n ) converges. We note the limit of the sequence ( v n ) (we will not try to calculate ) . What is the limit of the sequence ( u n ) ? E.3144 1 For any non-zero natural number n , consider the func-tion f n defined on 0 ; + by: f n ( x ) = ln x + x n 1 a Determine the limits of f n at 0 and + then study the direction of variations of f n . b Show that the equation f n ( x )=0 admits a single solu-tion in 0 ; + . Note ¸ n this solution. Show that it belongs to the interval 1 ; e . 2 The plane is referred to an orthonormal reference frame O ; i ; j ; k . We denote (Γ) the representative curve of the neperian logarithm function. a Let n be a non-zero natural number. Determine an equation of the line Δ n passing through the point A of coordinates (0 ; 1) and the point B n of coordinates ( n ; 0) . b Make a sketch representing the curve (Γ) and the straight lines Δ 1 , Δ 2 and Δ 3 . c Show that ¸ n is the abscissa of the point of intersection of (Γ) with Δ n . d Specify the value of ¸ 1 then make a conjecture about the direction of variation of the sequence ¸ n ) . 3 a Express ln( ¸ n ) as a function of n and ¸ n . b Express f n +1 ( ¸ n ) as a function of n and ¸ n and check that : f n +1 ( ¸ n ) < 0 c Deduce from the previous question the direction of variation of the sequence ( ¸ n ) . d Show that the sequence ( ¸ n ) converges. Let be its limit. Establish that ln =1 and deduce the value of . 4 We denote by D n the domain bounded by the curve (Γ) , the x-axis and the straight lines of equation : x = ¸ n and x =e . a Calculate the area of the domain D n as a function of ¸ n and show that this area is equal to ¸ 2 n n . b Establish that : (e ¸ n )ln ¸ n ¸ 2 n n (e ¸ n ) c Deduce a frame for n (e ¸ n ) . d is the general term sequence n (e ¸ n ) convergent? Does this result allow us to appreciate the speed of convergence of the sequence ( ¸ n ) ? 5. Unclassified financial years E.8144 Polynesia June 2018 https://chingmath.fr chapExoCorrec/3161 sacados/3161 chapExoCorrec/3144 sacados/3144 sacados/8144