Question 708316
(3c+d)/(cd^2) + (c-d)/(c^2d)
indeed, the LCD is c^2d^2:
(3c+d)/(cd^2)*c/c + (c-d)/(c^2d)*d/d
c(3c+d)/(c^2d^2) + d(c-d)/(c^2d^2)
(3c^2+cd)/(c^2d^2) + (cd-d^2)/(c^2d^2)
(3c^2+cd + cd-d^2)/(c^2d^2)
(3c^2+2cd-d^2)/(c^2d^2)
Notice:3c^2+2cd-d^2 factors as (3c-d)(c+d) (I think this is where you went wrong)
resulting in
(3c-d)(c+d)/(c^2d^2)