先化简再求值:3x2y-[2xy2-2(xy-32x2y)+xy]+3xy2,其中x=13,y=-5

先化简再求值:3x2y-[2xy2-2(xy-32x2y)+xy]+3xy2,其中x=13,y=-5.
2025-05-09 13:32:00
推荐回答(1个)
回答1:

原式=3x2y-[2xy2-(2xy-3x2y)+xy]+3xy2
=3x2y-(2xy2-2xy+3x2y+xy)+3xy2
=3x2y-2xy2+2xy-3x2y-xy+3xy2
=xy+xy2
当x=

1
3
,y=-5时,
原式=
1
3
×(-5)+
1
3
×25=
20
3