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Value of ∫23xx+5−xdx\int_2^3 \frac{\sqrt{x}}{\sqrt{x} + \sqrt{5-x}}dx is

Solution

✅ Correct Option: 2

Given:

∫23xx+5−xdx\int_2^3 \frac{\sqrt{x}}{\sqrt{x} + \sqrt{5-x}}dx


The King Property of definite integrals states:

∫abf(x)dx=∫abf(a+b−x)dx\int_a^b f(x)dx = \int_a^b f(a+b-x)dx

Here a=2a = 2 and b=3b = 3, so a+b=5a + b = 5.


Let I=∫23xx+5−xdxI = \int_2^3 \frac{\sqrt{x}}{\sqrt{x} + \sqrt{5-x}}dx ... (1)

Replacing xx with (5−x)(5-x):

I=∫235−x5−x+5−(5−x)dxI = \int_2^3 \frac{\sqrt{5-x}}{\sqrt{5-x} + \sqrt{5-(5-x)}}dx

I=∫235−x5−x+xdxI = \int_2^3 \frac{\sqrt{5-x}}{\sqrt{5-x} + \sqrt{x}}dx ... (2)


Adding equations (1) and (2):

I+I=∫23xx+5−xdx+∫235−xx+5−xdxI + I = \int_2^3 \frac{\sqrt{x}}{\sqrt{x} + \sqrt{5-x}}dx + \int_2^3 \frac{\sqrt{5-x}}{\sqrt{x} + \sqrt{5-x}}dx

2I=∫23x+5−xx+5−xdx2I = \int_2^3 \frac{\sqrt{x} + \sqrt{5-x}}{\sqrt{x} + \sqrt{5-x}}dx

2I=∫231 dx2I = \int_2^3 1 \, dx


2I=[x]232I = [x]_2^3

2I=3−22I = 3 - 2

2I=12I = 1

I=12I = \frac{1}{2}

Therefore, the value of the integral is 12\frac{1}{2}.

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