Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Evaluate the integral

  1. Aug 3, 2010 #1
    1. The problem statement, all variables and given/known data


    x2 sqrt(2+x3) dx

    2. Relevant equations

    3. The attempt at a solution

    Should I use substitution? Should I do it as a power?
  2. jcsd
  3. Aug 3, 2010 #2
    U substitution is the way to go for this one.
  4. Aug 4, 2010 #3


    User Avatar
    Science Advisor

    Since the only difficulty is that "[itex]2+ x^3[/itex]" inside the square root, let [itex]u= 2+ x^3[/itex] seems an obvious way to go.
  5. Aug 4, 2010 #4
    So when I substitute it as HallsofIvy suggested, what do I do with x2dx?


  6. Aug 4, 2010 #5


    User Avatar
    Science Advisor
    Homework Helper

    If u=2+x^3 isn't du=3*x^2*dx? Isn't that how substitution works?
  7. Aug 4, 2010 #6
    I am extremely confused with the next step of the solution.

    sqrt(u)du/(3x2) is this the correct substitution?
  8. Aug 4, 2010 #7


    User Avatar
    Science Advisor
    Homework Helper

    Well, no. What happened to the x^2 in your original problem? Isn't it x^2*sqrt(u)*(du/(3*x^2))?
  9. Aug 4, 2010 #8
    Thanks goodness, I got it.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook