题目内容：

(5x²-3y²)-[(5x²-2xy-y²)-(x²-2xy-y²)｝,其中x=2,y=-二分之一.先化简,后求值.

优质解答

(5x²-3y²)-[(5x²-2xy-y²)-(x²-2xy-y²)]＝5x²-3y²-[5x²-2xy-y²-x²+2xy+y²]＝5x²-3y²-[4x²]＝5x²-3y²-4x²＝x²-3y&#...