1. The problem statement, all variables and given/known data ∫∫ 1 / (2x + 3y), R = [0,1] x [1,2] 2. Relevant equations - Iterated integrals - u sub 3. The attempt at a solution Here is my attempt at solving this (I must be screwing up on the algebra) Integrating with respect to x u = 2x, dy = 2 u^-2 du u^-2 = - (1/u) [double chcked with wolfram alpha] ∫∫ (2x + 3y) ^ -2 -> -2 ∫ -(1/u) (2x + 3y) ^ -1 This is the part that stumps me....Sorry if I'm being vague. This is from Paul Online Notes Calculus III (http://tutorial.math.lamar.edu/Classes/CalcIII/IteratedIntegrals.aspx#MultInt_Iterated_Ex1d) THe part I want to understand is how they got -1/2 * ...... (2x+3y) ^ -1 Thanks!