Question

计算（-x-2y）∧2-（x-y+3）（x+y-3）-（2y-x）（x+3y）,

Answer 1

(-x-2y)^2-(x-y+3)(x+y-3)-(2y-x)(x+3y)

=(x+2y)^2-［x^2-(y-3)^2］+(x-2y)(x+3y)

=x^2+4xy+4y^2-x^2+y^2-6y+9+x^2+y-6y^2

=x^2+4xy-y^2-5y+9