Question

About integral
http://imgur.com/xtswv8H
Anyone pls tell me where 9x^2 is after the integral, I'm really bad at this >.<

Answer 1

that's called integral by u-sub

Answer 2

for int (3x^3 + 1)^(-3/2) 9x^2 dx
let u = 3x^3 + 1
du = 9x^2 dx

see that integral becomes
int (u)^-3/2 du

Answer 3

also, remember that the integral is nothing but the anti-derivative. meaning that if you derive the answer you should get back to what's in the integrand

Answer 4

does that make sense ?
@dangbeau

Answer 5

ah thank you so much, i got it now ^^

Answer 6

you're welcome :)