\(\int_2^7\frac{\sqrt{x}}{\sqrt{x}+\sqrt{9-x}}\,dx=\)
Q.1 (A) (iii) \(\int_2^7\frac{\sqrt{x}}{\sqrt{x}+\sqrt{9-x}}\,dx=\)
A. \(\frac{7}{2}\)
B. \(\frac{5}{2}\)
C. 7
D. 2
Q.1 (A) (iii) \(\int_2^7\frac{\sqrt{x}}{\sqrt{x}+\sqrt{9-x}}\,dx=\)
A. \(\frac{7}{2}\)
B. \(\frac{5}{2}\)
C. 7
D. 2
Best answer
Answer: B. \(\frac{5}{2}\)
Answer: (b) \(\frac{5}{2}\)
Let \(I=\int_2^7\frac{\sqrt{x}}{\sqrt{x}+\sqrt{9-x}}dx\). Using \(\int_a^bf(x)dx=\int_a^bf(a+b-x)dx\) with \(a+b=9\): \(I=\int_2^7\frac{\sqrt{9-x}}{\sqrt{9-x}+\sqrt{x}}dx\).
Adding, \(2I=\int_2^7 1\,dx=7-2=5\), so \(I=\frac{5}{2}\).
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