2(x^2-xy)-3(-2x^2-3xy)-2[x^2-(2x^2-xy+y^2)]

问题描述:

2(x^2-xy)-3(-2x^2-3xy)-2[x^2-(2x^2-xy+y^2)]

2(x^2-xy)-3(-2x^2-3xy)-2[x^2-(2x^2-xy+y^2)]

=2x²-2xy+6x²+9xy-2x²+4x²-2xy+2y²
=10x²+5xy+2y²