Question
Evaluate : $\int_1^2 \frac{\sqrt{x}}{\sqrt{3-x}+\sqrt{x}} d x$

Answer

Let $I =\int_1^2 \frac{\sqrt{x}}{\sqrt{3-x}+\sqrt{x}} d x$...(1)
$=\int_1^2 \frac{\sqrt{3-x}}{\sqrt{3-(3-x)}+\sqrt{3-x}} d x$
$\ldots \ldots\left\{\int_a^b f(x) d x=\int_a^b f(a+b-x) d x\right\}$
$I=\int_1^2 \frac{\sqrt{3-x}}{\sqrt{x}+\sqrt{3-x}} d x$...(2)
Adding (1) and (2)
$2 I =\int_1^2 \frac{\sqrt{x}+\sqrt{3-x}}{\sqrt{x}+\sqrt{3-x}} d x$
$=\int_1^2 1 d x=[x]_1^2$
$\therefore \quad 2 I =2-1=1$
$\therefore \quad I=\frac{1}{2}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free