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

问题描述:

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

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