Question

9x·x-x·x-2xy-y如何因式分解？

Answer 1

原式
=9x^2-x^2-2xy-y
=8x^2-2xy-y
没有公因数，不能因式分解。

Answer 2

=x²-xy-xy+y²+x-y
=（x²-xy）-（xy-y²)+(x-y)
=x(x-y)-y(x-y)+(x-y)
=(x-y+1)(x-y)