Question

The function $$f\left( x \right) = \int_{ - 1}^x {t\left( {{e^t} - 1} \right){{\left( {t - 2} \right)}^3}{{\left( {t - 3} \right)}^5}} dt$$         has a local minimum at $$x$$ which is equal to :

A. 0
B. 1
C. 2
D. 3  
Answer :   3
Solution :
$$\eqalign{ & f'\left( x \right) = x\left( {{e^x} - 1} \right){\left( {x - 2} \right)^3}.{\left( {x - 3} \right)^5} \cr & f'\left( {0 - \in } \right) = \left( {0 - \in } \right)\left( {{e^{0 - \in }} - 1} \right){\left( {0 - \in - 2} \right)^3}{\left( {0 - \in - 3} \right)^5} = \left( { + {\text{ve}}} \right) \cr & f'\left( {0 + \in } \right) = \left( {0 + \in } \right)\left( {{e^{0 + \in }} - 1} \right){\left( {0 + \in - 2} \right)^3}{\left( {0 + \in - 3} \right)^5} = \left( { + {\text{ve}}} \right) \cr & f'\left( {1 - \in } \right) = \left( {1 - \in } \right)\left( {{e^{1 - \in }} - 1} \right){\left( {1 - \in - 2} \right)^3}{\left( {1 - \in - 3} \right)^5} = \left( { + {\text{ve}}} \right) \cr & f'\left( {1 + \in } \right) = \left( {1 + \in } \right)\left( {{e^{1 + \in }} - 1} \right){\left( {1 + \in - 2} \right)^3}{\left( {1 + \in - 3} \right)^5} = \left( { + {\text{ve}}} \right) \cr & f'\left( {2 - \in } \right) = \left( {2 - \in } \right)\left( {{e^{2 - \in }} - 1} \right){\left( {2 - \in - 2} \right)^3}{\left( {2 - \in - 3} \right)^5} = \left( { + {\text{ve}}} \right) \cr & f'\left( {2 + \in } \right) = \left( {2 + \in } \right)\left( {{e^{2 + \in }} - 1} \right){\left( {2 + \in - 2} \right)^3}{\left( {2 + \in - 3} \right)^5} = \left( { - {\text{ve}}} \right) \cr & {\text{so, a local maximum at }}x = 2 \cr & f'\left( {3 - \in } \right) = \left( {3 - \in } \right)\left( {{e^{3 - \in }} - 1} \right){\left( {3 - \in - 2} \right)^3}{\left( {3 - \in - 3} \right)^5} = \left( { - {\text{ve}}} \right) \cr & f'\left( {3 + \in } \right) = \left( {3 + \in } \right)\left( {{e^{3 + \in }} - 1} \right){\left( {3 + \in - 2} \right)^3}{\left( {3 + \in - 3} \right)^5} = \left( { + {\text{ve}}} \right); \cr & {\text{so, a local minimum at }}x = 3 \cr} $$

Releted MCQ Question on
Calculus >> Application of Integration

Releted Question 1

The area bounded by the curves $$y = f\left( x \right),$$   the $$x$$-axis and the ordinates $$x = 1$$  and $$x = b$$  is $$\left( {b - 1} \right)\sin \left( {3b + 4} \right).$$     Then $$f\left( x \right)$$  is-

A. $$\left( {x - 1} \right)\cos \left( {3x + 4} \right)$$
B. $$\sin \,\left( {3x + 4} \right)$$
C. $$\sin \,\left( {3x + 4} \right) + 3\left( {x - 1} \right)\cos \left( {3x + 4} \right)$$
D. none of these
Releted Question 2

The area bounded by the curves $$y = \left| x \right| - 1$$   and $$y = - \left| x \right| + 1$$   is-

A. $$1$$
B. $$2$$
C. $$2\sqrt 2 $$
D. $$4$$
Releted Question 3

The area bounded by the curves $$y = \sqrt x ,\,2y + 3 = x$$    and $$x$$-axis in the 1st quadrant is-

A. $$9$$
B. $$\frac{{27}}{4}$$
C. $$36$$
D. $$18$$
Releted Question 4

The area enclosed between the curves $$y = a{x^2}$$   and $$x = a{y^2}\left( {a > 0} \right)$$    is 1 sq. unit, then the value of $$a$$ is-

A. $$\frac{1}{{\sqrt 3 }}$$
B. $$\frac{1}{2}$$
C. $$1$$
D. $$\frac{1}{3}$$

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