I have a homework problem that I do not know how to begin. I must evaluate integral (4/3x+7) dx. I think u= 3x+7 but beyond that I am just lost. Would du = 4x? Please help. Solution yeah, u = 3x + 7 du = 3 dx then substitute it, int 4 dx / ( 3x + 7) = int 4 du / 3 u = 4/3 int du/u = 4/3 ln u = 4/3 ln ( 3x + 7) + C.