5xy-[x的平方+4xy-y的平方-（x的平方+2xy-2y的平方）]=5xy-(x²+4xy-y²-x²-2xy+2y²)=5xy-(2xy+y²)=5xy-2xy-y²=3xy-y²当x=-2,y=-1时原式=3×(-2)(-1)-(-1)²=6-1=5...