Question

Let $$P\left( x \right) = {a_0} + {a_1}{x^2} + {a_2}{x^4} + ..... + {a_n}{x^{2n}}$$         be a polynomial in a real variable $$x$$ with $$0 < {a_0} < {a_1} < {a_2} < ..... < {a_n}.$$       The function $$P\left( x \right)$$  has :

A. neither a maximum nor a minimum
B. only one maximum
C. only one minimum  
D. only one maximum and only one minimum
Answer :   only one minimum
Solution :
The given polynomial is
$$P\left( x \right) = {a_0} + {a_1}{x^2} + {a_2}{x^4} + ..... + {a_n}{x^{2n}},\,x\, \in \,R{\text{ and }}\,0 < {a_0} < {a_1} < {a_2} < ..... < {a_n}.$$
Here, we observe that all coefficients of different powers of $$x,$$ i.e., $${a_0},\,{a_1},\,{a_2},\,.....,{a_n},$$     are positive.
Also, only even powers of $$x$$ are involved.
Therefore, $$P\left( x \right)$$  cannot have any maximum value.
Moreover, $$P\left( x \right)$$  is minimum, when $$x = 0,$$  i.e., $${a_0}.$$
. Therefore, $$P\left( x \right)$$  has only one minimum.

Releted MCQ Question on
Calculus >> Application of Derivatives

Releted Question 1

If  $$a + b + c = 0,$$    then the quadratic equation $$3a{x^2}+ 2bx + c = 0$$     has

A. at least one root in $$\left[ {0, 1} \right]$$
B. one root in $$\left[ {2, 3} \right]$$  and the other in $$\left[ { - 2, - 1} \right]$$
C. imaginary roots
D. none of these
Releted Question 2

$$AB$$  is a diameter of a circle and $$C$$ is any point on the circumference of the circle. Then

A. the area of $$\Delta ABC$$  is maximum when it is isosceles
B. the area of $$\Delta ABC$$  is minimum when it is isosceles
C. the perimeter of $$\Delta ABC$$  is minimum when it is isosceles
D. none of these
Releted Question 3

The normal to the curve $$x = a\left( {\cos \theta + \theta \sin \theta } \right),y = a\left( {\sin \theta - \theta \cos \theta } \right)$$        at any point $$'\theta '$$ is such that

A. it makes a constant angle with the $$x - $$axis
B. it passes through the origin
C. it is at a constant distance from the origin
D. none of these
Releted Question 4

If $$y = a\ln x + b{x^2} + x$$     has its extremum values at $$x = - 1$$  and $$x = 2,$$  then

A. $$a = 2,b = - 1$$
B. $$a = 2,b = - \frac{1}{2}$$
C. $$a = - 2,b = \frac{1}{2}$$
D. none of these

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Application of Derivatives


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