1.

Find the integral of \(\frac{5x^4}{\sqrt{x^5+9}}\).(a) \(\sqrt{x^5+9}\)(b) \(2\sqrt{x^5-9}\)(c) 2(x^5+9)(d) \(2\sqrt{x^5+9}\)I have been asked this question in examination.This intriguing question comes from Methods of Integration-1 in portion Integrals of Mathematics – Class 12

Answer»

Correct OPTION is (d) \(2\SQRT{x^5+9}\)

For explanation I would say: Let x^5+9=t

Differentiating w.r.t x, we get

5x^4 dx=dt

\(\INT \frac{5x^4}{\sqrt{x^5+9}} dx=\int \frac{dt}{\sqrt{t}}\)

=\(\frac{t^{-\frac{1}{2}+1}}{-\frac{1}{2}+1}=2\sqrt{t}\)

REPLACING t with x^5+9, we get

\(\int \frac{5x^4}{\sqrt{x^5+9}} dx=2\sqrt{x^5+9}\).



Discussion

No Comment Found

Related InterviewSolutions