Выражение а) 3a(a+1)+(a+2)(a-3) б) (y-4) в 2 степени -(4-y)(4+y)

А) 3a(a+1)+(a+2)(a-3)= 3а^2 +3a + a^2-3a +2a -6 = 4a^2 +2a -6
б)(y-4)^2 -(4-y)(4+y) = y^2 - 8y +16 -(16-y^2) = y^2 -8y +16 -16 +y^2 = 2y^2-8y = 2y(y-4)