How do you find the integral of dx/((x^(5/2) * (1+ x^2)^(1/4))dx(x52(1+x2)14)?

1 Answer
Jul 21, 2018

int1/(x^(5/2)(1+x^2)^(1/4))dx=-2/3(1/x^2+1)^(3/4)+c1x52(1+x2)14dx=23(1x2+1)34+c

Explanation:

Here ,

I=int1/(x^(5/2)(1+x^2)^(1/4))dxI=1x52(1+x2)14dx

Substitute color(red)(x=1/t=>dx=-1/t^2dtx=1tdx=1t2dt

So,

I=int1/((1/t)^(5/2)(1+1/t^2)^(1/4))(-1/t^2)dtI=1(1t)52(1+1t2)14(1t2)dt

=-intt^(5/2)/((t^2+1)^(1/4)/t^(1/2))*1/t^2dt=t52(t2+1)14t121t2dt

=-intt^(5/2+1/2-2)/(t^2+1)^(1/4)dt=t52+122(t2+1)14dt

:.I=-intt/(t^2+1)^(1/4)dt

Substitute color(blue)((t^2+1)^(1/4)=u=>t^2+1=u^4

=>2tdt=4u^3du=>tdt=2u^3du

I=-int(2u^3)/udu

=>I=-2intu^2du

=>I=-2[u^3/3]+c

=-2/3(u)^3+c

Subst. back , color(blue)(u=(t^2+1)^(1/4)

I=-2/3(t^2+1)^(3/4)+c

Again subst. color(red)(t=1/x

:.I=-2/3(1/x^2+1)^(3/4)+c

=>I=-2/3(1+x^2)^(3/4)/(x^2)^(3/4)+c

:.I=-(2(1+x^2)^(3/4))/(3x^(3/2))+c