1. The problem statement, all variables and given/known data ∫(1/x^(2))(3+1/x)^(3) 2. Relevant equations U substitution is the way to go here 3. The attempt at a solution My problem is that I cant figure my du and what is next. I know which one it is but I don't know the reason for it. u=3+1/x du= I chose ln|x| first but that got me nowhere. My buddy told me (txt) me it is -1/x^(2) wich eventually takes you to -(u)^4/4 but i cant figure out what happened in between. thanks for the hand.