4xy-[(x²+5xy-y²)-(x²+3xy-2y²)],其中x=2,y=-1求值与化简
问题描述:
4xy-[(x²+5xy-y²)-(x²+3xy-2y²)],其中x=2,y=-1求值与化简
答
4xy-[(x²+5xy-y²)-(x²+3xy-2y²)]
=4xy-x²-5xy+y²+x²+3xy-2y²
=2xy-y²
=-2x1-(-1)²
=-2-1
=-3