# Math Help - Question

1. ## Question

Looking at some of the older stuff and for ∫1/10(x)(6x^2-15) dx became 1/120 ∫12x(6x^2-15) dx, how was the 1/120 ∫12x arrived at?

2. ## Re: Question

1/10 = 1/120 * 12
and we know that you can move a constant outside of the integral

3. ## Re: Question

I can see that but why 12?

4. ## Re: Question

probably to make u-substitution more straightforward

i.e.
u=6x^2-15
du=12x dx

5. ## Re: Question

Not sure if I quite get it but thanks

6. ## Re: Question

EDIT:
1/120 ∫12x(6x^2-15) dx
=1/120
∫ 72x^3-180x dx

I'm sorry i forgot that it was possible that you didn't cover u-substitution, which is just a method of integration and all you had to do was multiply it out and integrate the polynomial! sorry!
and 1/120 was probably to avoid fractions during integration

7. ## Re: Question

Thanks for that I have to get used to such manipulation, I have never been on one of these forums before and can not figure out how to do a smiley face

8. ## Re: Question

Originally Posted by landmark
Thanks for that I have to get used to such manipulation, I have never been on one of these forums before and can not figure out how to do a smiley face
The usual way: = : + )

-Dan