x的二次方y-xy的二次方-(2x的二次方+4xy+2y的二次方)=x²y-xy²-(2x²+4xy+2y²)=xy(x-y)-2(x+y)²已知x-y=-3,x+y=1;(x+y)²-(x-y)²=1-9=-8=4xy;xy=-2;原式=(-2)(-3)-2*1*1=6-2=4;...