化简,得:
=(1/2)x²y-[(3/2)x²y-3xyt+2x²y+x²y]-3xyt
=(1/2)x²y-(3/2)x²y+3xyt-2x²y-x²y-3xyt
=[(1/2)-(3/2)-2-1]x²y
=-4x²y
这个式子的值与t无关.