Question

已知x的平方-Xy=60,xy-y的平方=40,求代数式x的平方-y的平方和2x的平方-5xy+3y的立方的值

Answer 1

x^2-y^2

=x^2-xy+xy-y^2

=60+40

=100

2x^2-5xy+3y^2

=2(x^2-2xy)-3(xy-y^2)

=2*60-3*40

=120-120

=0