1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Help! I'm in college and have forgotten everything!

  1. Sep 15, 2006 #1
    Hi. I am in college and have forgotten everything about how to solve indefinite integrals.

    Even very simple problems give me trouble, such as:

    int( y^3 * sqrt(2y^4 - 1) ) dy

    So how in the world do you find the answer? The Antiderivative? Please go through this step-by-step, I need a good jumpstart to get myself in the right frame of mind again.
  2. jcsd
  3. Sep 15, 2006 #2
    So you have [tex] \int y^{3}\sqrt{2y^{4}-1} dy [/tex]. Let [tex] u = 2y^{4} -1 [/tex], then [tex] du = 8y^{3} dy [/tex]. But there is only a [tex] y^{3} dy [/tex] available so we have to multiply the integral by [tex]\frac{1}{8} [/tex]:

    [tex] \frac{1}{8} \int u^{\frac{1}{2}} du = \frac{1}{12}(2y^{4}-1)^\frac{3}{2} + C [/tex]
    Last edited: Sep 15, 2006
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook