Question

已知x2-xy=-3,2xy-y2=-8,求 (1)x2+xy-y2 (2)2x2+4xy-3y2 字母后面直接跟数字的

Answer 1

1.x²+xy-y²

=x²-xy+2xy-y²

=-3+(-8)

=-11

2.2x²+4xy-3y²

=2(x²-xy)+3(2xy-y²)

=-6-24

=-30