Results 1 to 8 of 8

Math Help - Question

  1. #1
    Newbie
    Joined
    Feb 2013
    From
    Ireland
    Posts
    15

    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?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Newbie
    Joined
    Feb 2013
    From
    Toronto
    Posts
    3

    Re: Question

    1/10 = 1/120 * 12
    and we know that you can move a constant outside of the integral
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Feb 2013
    From
    Ireland
    Posts
    15

    Re: Question

    I can see that but why 12?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Feb 2013
    From
    Toronto
    Posts
    3

    Re: Question

    probably to make u-substitution more straightforward

    i.e.
    u=6x^2-15
    du=12x dx
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Feb 2013
    From
    Ireland
    Posts
    15

    Re: Question

    Not sure if I quite get it but thanks
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Newbie
    Joined
    Feb 2013
    From
    Toronto
    Posts
    3

    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
    Last edited by coffee2000; February 22nd 2013 at 02:39 PM.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Newbie
    Joined
    Feb 2013
    From
    Ireland
    Posts
    15

    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
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    10,054
    Thanks
    368
    Awards
    1

    Re: Question

    Quote Originally Posted by landmark View Post
    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
    Follow Math Help Forum on Facebook and Google+

Search Tags


/mathhelpforum @mathhelpforum