Question

3(xy²-x²y)-2(xy+ xy²)+3x²y怎么做

3xy²-2(xy-3/2x²y)+(3x²y-2xy²),其中,x=-2,y=1/2
挺急的,答对再追加10、
先化简，再求值

Answer 1

解原式
=3xy²-2(xy-3/2x²y)+(3x²y-2xy²)
=3xy²-2xy+3x²y+3x²y-2xy²
=xy²+6x²y-2xy
=xy(y+6x-2）
=（-2）×（1/2)[1/2+6×（-2）-2]
=-（1/2-14)
=14-1/2
=27/2