-(x2+y2)+[-3xy-(x2-y2)],其中x =-1,y =2.
问题描述:
-(x2+y2)+[-3xy-(x2-y2)],其中x =-1,y =2.
答
-(x2+y2)+[-3xy-(x2-y2)]
=-x²-y²-3xy-x²+y²
=-2x²-3xy
=-2×(-1)²-3×(-1)×2
=4