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: U substitution

  1. Sep 10, 2007 #1
    First day of u subs...

    [tex]\int t \sqrt{7t^2+12}dt[/tex]

    I am assuming that u=t, but It is maiking a mess when I do that.

    Just a hint please,
  2. jcsd
  3. Sep 10, 2007 #2
    your first choice on a u-substitution with a rational number should always be the entire thing under the square root.

    try u=7*t^2+12 instead
  4. Sep 10, 2007 #3
    let u be the radican (is that the proper term? i forget) :D
  5. Sep 10, 2007 #4
    do you mean like this?

    If I do this, I get [tex]\int tudt[/tex] and [tex]du=\frac{dt}{2\sqrt{7t^2+12}}[/tex] ...right?

    I think I am confused...
  6. Sep 10, 2007 #5
    no just the 7t^2+12

    if u=7t^2+12
    what is dt=??
  7. Sep 10, 2007 #6
    Oh..one sec...
  8. Sep 10, 2007 #7
    Brain Cramp![tex]u=7t^2+12[/tex]
    [tex]\int t u^{1/2} dt *14*\frac{1}{14}[/tex]
    [tex]=\frac{1}{14}\int \sqrt{u}* du[/tex]
    and I got it from here..
    Thanks guys,
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook