化简求值:3x的平方y-3y的平方x+2xy的平方-2x的平方y,其中x=1/2,y=负1.

3x²y-3y²x+2xy²-2x²y
=3x²y-2x²y-3xy²+2xy²
=x²y-xy²
=xy(x-y)
=1/2*(-1)*[1/2-(-1)]
=-1/2*3/2
=-3/4