a^3+2ab^2+3a^2b+28b^3 = a^3+3a^2b + 2ab^2 + 28b^3 = a(a^2+3ab) + 2b^2(a+14b) = a(a+3b)(a)+ 2b(a+14b) = (a+3b)(a^2+2b)
a^3+2ab^2+3a^2b+28b^3 = a^3+3a^2b + 2ab^2 + 28b^3 = a(a^2+3ab) + 2b^2(a+14b) = a(a+3b)(a)+ 2b(a+14b) = (a+3b)(a^2+2b)