5xy2-{2x2y-[3xy2-(4xy2-2xy2)]},其中x=2,y=-1.
问题描述:
5xy2-{2x2y-[3xy2-(4xy2-2xy2)]},其中x=2,y=-1.
答
原式=5xy2-{2x2y-[3xy2-4xy2+2xy2]}=5xy2-{2x2y-xy2}=5xy2-2x2y+xy2=6xy2-2x2y,
当x=2,y=-1时,
原式=6×2×1-2×4×(-1)=20.