Grade 12 - Comp. / Annales intégrales 6 exercises (100% corrected)

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xxyy-0,200,20,40,60,811,2-0,20,20,40,60,811,21,41,61,822,22,42,6CgCf 1. Integrals E.7733 A company manufactures wire-less speakers. The production cost of a speaker is 300 euros. Let x be the selling price of a speaker in hundreds of euros. Market research allows us to model the situation : for any real number x in the interval 3 ; 10 , if the selling price of a speaker is x hundred euros, then the number of buyers is modeled by: f ( x ) = e 0.25 · x +5 Thus, f ( x ) is an approximation of the number of buyers for a selling price of x hundred euros. For example, if the selling price of a speaker is set at 400 euros, the number of buyers is approximated by f (4) . 1 Give an approximate value for the number of buyers for a selling price of 400 dollars. The difference between the amount obtained from the sale of the speakers and their production cost is called the gross margin. 2 What is the gross margin of this company for a selling price of 400 euros per speaker? Let g ( x ) be the gross margin, in hundreds of euros, achieved by the company for a selling price of x hundreds of euros per speaker. 3 Show that for any real number x belonging to the interval 3 ; 10 : g ( x ) = x 3 · e 0.25 · x +5 4 A computer algebra system gives the following results : factorize(derive[(x-3)*exp(-0.25*x+5)]) x 7 4 · e 1 4 x +5 a Using the result from the computer algebra software, study the variations of the function g on the interval 3 ; 10 . b At what unit selling price will the company achieve the maximum gross margin? Give the value of this gross margin rounded to the nearest euro. 5 Let G be the function such that G ( x )= 4 · x 4 · e 0.25 · x +5 for all real numbers x of 3 ; 10 . a Show that G is a primitive of the function g . b Let I = 10 3 g ( x ) d x . Determine the exact value of I . E.7429 A company wants to use a deco-rative pattern for its communications. To create this pattern, its shape is modeled using two func-tions f and g defined for any real number x of 0 ; 1 by: f ( x ) = 1 x · e 3 x ; g ( x ) = x 2 2 · x + 1 Their representative curves will be denoted C f and C g . Part A A computer algebra system gives the following results : Derive (1-x)*exp(3x) :-3x*exp(3*x)+2exp(3*x) factorize -3*xexp(3*x)+2*exp(3*x) :exp(3x)*(-3x+2) factorize(derive(exp(3x)(-3x+2))) :3*exp(3*x)(1-3x) Reading : the derivative of the function f is given by: f ( x )= 3 x · e 3 x +2 · e 3 x , which, after factorization, gives : f ( x )= 3 x +2 · e 3 x 1 Study the sign of the derivative function f on 0 ; 1 , then give the table of variations of f on 0 ; 1 , specify-ing the useful values. 2 The curve C f has an inflection point. Determine its co-ordinates. Part B We want to calculate the area of the shaded part of the graph. 1 Check that points A and B , with coordinates (1 ; 0) and (0 ; 1) respectively, are points common to curves C f and C g . 2 We assume that : for all x in 0 ; 1 : f ( x ) g ( x ) = 1 x · e 3 x 1 + x a Justify that for all x in 0 ; 1 : e 3 x 1 0 b Deduce that for all x in 0 ; 1 : e 3 x 1+ x 0 c Study the sign of f ( x ) g ( x ) for all x in 0 ; 1 3 a Calculate 1 0 g ( dx ) d x . b We assume that : 1 0 f ( x ) d x = e 3 4 9 Calculate the area S , in area units, of the shaded part. https://chingmath.fr chapExoCorrec/7733 sacados/7733 chapExoCorrec/7429 sacados/7429 xxyy-0,200,20,40,60,811,2-0,20,20,40,60,811,21,41,61,822,22,42,6CgCf
a01123456C 2345678I2345678910111213141516JOC Round the result to the nearest tenth. E.6989 Consider the function f defined on the interval 0 ; 1 by: f ( x )=4+e 5 x The curve C representative of the function f has been plotted in a planar coordinate system. The hatched area D on the figure is the area bounded by the curve C , by the x-axis, the y-axis and the straight line of equation x =1 . We want to divide the hatched domain into two domains of equal area by a straight line of equation y = a , parallel to the x-axis, according to the example given below. 1 Justify that the value a =3 is not suitable. 2 Determine to the nearest 0.1 a suitable value of a . 2. Integrals and the intermediate value theorem E.6974 The two parts of this exercise are independent. Part A In this part, answers will be given without justification, with the precision allowed by the graph below : This graph shows, in a coordinate system with origin O , the representative curve C of a function f defined and differen-tiable on the interval 0 ; 7 . 1 Enclose each of the solutions to the equation f ( x )=10 on the interval 0 ; 7 between two consecutive integers. 2 Give the maximum value of the function f on the interval 0 ; 7 and specify the value at which it is reached. 3 The value of the integral 3 1 f ( x ) d x belongs to only one of the following intervals. Which one? a 9 ; 17 b 18 ; 26 c 27 ; 35 Part B The curve given in part A. is the representation of the func-tion f defined and differentiable on the interval 0 ; with expression : f ( x ) = 2 · x · e x +3 Recall that f denotes the derivative of the function f . 1 Show that for any real number x in the interval 0 ; 7 : f ( x ) = 2 x + 2 · e x +3 2 a Study the sign of f ( x ) on the interval 0 ; 7 and then deduce the table of variations of the function on this same interval. b Calculate the maximum value of the function f on the interval 0 ; 7 3 a Justify that the equation f ( x )=10 has two solutions on the interval 0 ; 7 , which we will denote by ¸ and ˛ with ¸<˛ . b We assume that ¸ 0.36 to 10 2 . Give the value of ˛ , rounded to 10 2 . 4 Consider the function F defined on the interval 0 ; 7 by: F ( x ) = 2 x 2 · e x +3 a Justify that F is a primitive of f on the interval 0 ; 7 . b Calculate the exact value of the area, in area units, of the plane domain bounded by the lines with equations x =1 , x =3 , the x-axis, and the curve C . https://chingmath.fr chapExoCorrec/6989 sacados/6989 Antilles Juin 2017 a01123456C chapExoCorrec/6974 sacados/6974 2345678I2345678910111213141516JOC
234567I23456789JOAB 5 The function f studied models a company’s profit, in thousands of euros, from the sale of x hundreds of items ( x between 0 and 7 ) . a Calculate the average profit, to the nearest euro, when the company sells between 100 and 300 items. b The company wants its profit to be greater than 10 000 euros. Determine the number of items the company will need to sell to achieve its goal. 3. Integrals and convexity E.6978 Let f be a function defined on the interval 0.7 ; 6 ; we assume that f is differentiable. Part A : graphical analysis The function f is represented in the graph below. 1 The tangent at the point with abscissa 3 to the curve representing f passes through the points A (3 ; 4) and B (4 ; 0) . Determine f (3) . 2 Based on the graph above, give the table of signs for f on the interval 0.7 ; 6 . Part B: theoretical study We assume that the function f is defined by: f ( x ) = x 2 2 · x + 1 · e 2 x +6 1 Show that : f ( x ) = 2 x 2 + 6 x 4 · e 2 x +6 where f denotes the derivative of the function f . 2 Study the direction of variation of the function f on the interval 0.7 ; 6 and draw up a table of variations of the function f on the interval 0.7 ; 6 . You are not required to calculate the ordinates. 3 Using computer algebra software, we obtain the results below, which can be used without being proven. L1 f’(x):=(-2x^2+6x-4)*e^(-2x+6) ↦→ f ( x ) = ( 2 x 2 + 6 x 4)e 2 x +6 L2 g(x):=Dérivée[f’(x)] ↦→ g ( x ) = 16 x e 2 x +6 + 4 x 2 e 2 x +6 + 14e 2 x +6 L3 Factoriser[g(x)] ↦→ 2e 2 x +6 2 x 2 8 x + 7 L4 Résoudre[g(x)=0] ↦→ x = 2+4 2 ; x = 2+4 2 L5 F(x):=Primitive[f(x)] ↦→ F ( x ) = 1 4 2 x 2 + 2 x 1 e 2 x +6 a Determine the largest interval over which the function f is concave b Does the graph of the function f have any inflection points? If so, give their x-coordinates. c We set I = 5 3 f ( x ) d x . Calculate the exact value of I , then the value rounded to 10 1 . 4. Integrals, intermediate value theorem and convexity E.6988 The curve C below is the repre-sentative curve in the plane equipped with an orthonormal coordinate system of a function f defined and twice differen-tiable on the interval 4 ; 10 . We denote f as the derivative of f , and f  as its second derivative. The tangent to the curve C at point A with abscissa 2 is parallel to the abscissa axis. The shaded area S in the figure is the area between the curve C , the x-axis, the line with equation x =2 , and the line with equation x =4 . https://chingmath.fr chapExoCorrec/6978 sacados/6978 234567I23456789JOAB chapExoCorrec/6988 sacados/6988 Antilles Juin 2017
-5-4-3-2-101234567891011-1123456C Part A 1 Determine the value of f ( 2) and justify your answer. 2 Based on the graph, what does the sign of f (4) appear to be? 3 Using the graph, determine a range of two consecutive integers for the area of the shaded region S in the figure. Part B The previous function f is defined on the interval 4 ; 10 by: f ( x ) = x + 4 · e 0.5 x 1 a Show that : f ( x )= 0.5 · x 1 · e 0.5 x b Study the variations of the function f on the interval 4 ; 10 . c Show that on the interval 1 ; 6 , the equation f ( x )= 1.5 has a unique solution. Let us denote this unique solution by ¸ . d Donner of ¸ , rounded to 10 2 of ¸ 2 On admit that the second derivative of f is defined by: f  ( x ) = 0.25 · x · e 0.5 x a Étudier the convexity of the function f on the interval 4 ; 10 . b Deduce that the curve C admits a single point of in-flection I whose coordinates will be calculated. 3 a On consider the function F defined by: F ( x )= 2 x 12 · e 0.5 x How can we show that F is a primitive of f on the interval 4 ; 10 ? This check is not required. b Calculate: S = 4 2 f ( x ) d x . Give the exact value and then the value rounded to the hundredth. https://chingmath.fr -5-4-3-2-101234567891011-1123456C