Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Applications of Derivatives

Question:

From mean value theorem: $f(b)-f(a)=(b-a) f'\left(x_1\right) ; a<x_1<b$ if $f(x)=\frac{1}{x'}$ then $x_1=$

Options:

$\sqrt{a b}$

$\frac{a+b}{2}$

$\frac{2 a b}{a+b}$

$\frac{b-a}{b+a}$

Correct Answer:

$\sqrt{a b}$

Explanation:

Since $f(x)=\frac{1}{x}$

$f'\left(x_1\right)=\frac{f(b)-f(a)}{b-a}$

$\Rightarrow -\frac{1}{x_1^2}=\frac{1 / b-1 / a}{b-a}$

$\Rightarrow x_1=\sqrt{a b}$