化简求值:[x(x2y2-xy)-y(x2-x3y)]÷3x2y,其中x=3,y=-1.
问题描述:
化简求值:[x(x2y2-xy)-y(x2-x3y)]÷3x2y,其中x=3,y=-1.
答
原式=[x3y2-x2y-x2y+x3y2]÷3x2y
=(2x3y2-2x2y)÷3x2y
=
xy-2 3
;2 3
当x=3,y=-1时,
原式=
×3×(-1)-2 3
=-2 3
.8 3