问题
解答题
先化简,再求值 3x2y-[2xy-2(xy-
|
答案
原式=3x2y-[2xy-2xy+3x2y+xy],
=3x2y-3x2y-xy,
=-xy,
当x=3,y=-
时,原式=-3×(-1 3
)=1.1 3
先化简,再求值 3x2y-[2xy-2(xy-
|
原式=3x2y-[2xy-2xy+3x2y+xy],
=3x2y-3x2y-xy,
=-xy,
当x=3,y=-
时,原式=-3×(-1 3
)=1.1 3