1/2x^2y-[3/2x^2y-3(xyt-2/3x^2y)+yx^2]-3xyt
=1/2x^2y-3/2x^2y+3(xyt-2/3x^2y)-yx^2-3xyt
=-2x^2y+3(xyt-2/3x^2y)-3xyt
=-2x^2y+3xyt-2x^2y-3xyt
=-4x^2y
所以和t没关系
1/2x^2y-[3/2x^2y-3(xyt-2/3x^2y)+yx^2]-3xyt
=1/2x^2y-3/2x^2y+3(xyt-2/3x^2y)-yx^2-3xyt
=-2x^2y+3(xyt-2/3x^2y)-3xyt
=-2x^2y+3xyt-2x^2y-3xyt
=-4x^2y
所以和t没关系