1. The problem statement, all variables and given/known data let f be continuous on [0,1] and let R be triangular region with vertices (0,0),(1,0) and (0,1) show that[tex]\int\intf(x+y) dA[/tex]= [tex]\intu*f(u)du[/tex] from 0 to 1 2. Relevant equations 3. The attempt at a solution i dont know how to start this question. can anyone give me a hint to help me start this question?