-5y^3(y-6)+4y^3(y-7)

Question

OK - first, distribute -5y^3 to the (y-6). You should get -5y^4+30y^3. Do the same thing by distributing 4y^3 to the (y-7), leaving you with 4y^4-28y^3. Then combine the y^4 terms and the y^3 terms to get the answer of -y^4+2y^3.