8(a+2b)^2(a-b)+18(b-a)^3
=8(a+2b)^2(a-b)-18(a-b)^3
=2(a-b)[4(a+2b)^2-9(a-b)^2]
=2(a-b)[(2(a+2b)+3(a-b)][2(a+2b)-3(a-b)]
=2(a-b)(5a+b)(-a+7b)
8(a+2b)^2(a-b)+18(b-a)^3
=8(a+2b)^2(a-b)-18(a-b)^3
=2(a-b)[4(a+2b)^2-9(a-b)^2]
=2(a-b)[(2(a+2b)+3(a-b)][2(a+2b)-3(a-b)]
=2(a-b)(5a+b)(-a+7b)