1a, 3x²-12x+12=3x²-6x-6x+12=3x(x-2)-6(x-2)=(x-2)(3x-6)=3(x-2)²
b,(x²-y²)+(7x+7y)=(x-y)(x+y)+7(x+y)=(x+y)(x-y+7)
c, x²-3xy+2xy-6y²=x(x-3y)+2y(x-3y)=(x-3y)(x+2y)
d,x³+2x²-5x²-10x+4x+8=x²(x+2)-5x(x+2)+4(x+2)=(x²-5x+4)(x+2)=(x²-4x-x+4)(x+2)=(x(x-4)-(x-4))(x+2)=(x-1)(x-4)(x+2)