2x²+7x+3
=2x²+6x+x+3
=2x(x+3)+(x+3)
=(x+3)(2x+1)
x²-3xy+2y²
=x²-2xy-xy+2y²
=x(x-2y)-y(x-2y)
=(x-2y)(x-y)(x²-3x)²-2(x-3x)-8原式=(x²-3x-4)(x²-3x+2)=(x-4)(x+1)(x-1)(x-2)(x²-3x-4)(x²-3x+2)这部什么意思x²-3x看做整体别问了