Question

1、9（2x-y）²-16（x+2y）² 2、-14xy-x²-49y² 3、（

Answer 1

解

9(2x-y)²-16(x+2y)²

=[3(2x-y)-4(x+2y)][3(2x-y)+4(x+2y)]

=(6x-3y-4x-8y)(6x-3y+4x+8y)

=(2x-11y)(10x+5y)

=5(2x-11y)(2x+y)

-14xy-x²-49y²

=-(x²+14xy+49y²)

=-(x+7y)²

(x²-2x)²-2x(2-x)+1

=(x²-2x²)²+2(x²-2x)+1

=[(x²-2x)+1]²

=(x²-2x+1)²

=[(x-1)²]²

=(x-1)^4