试说明 x的立方*y的立方-1/2*x的平方*y+y的平方-2*x的立方*y的立方+0.5*x的平方*y+y的平方+x的立方*y的立方-2y-7的值语字母x的取值无关.

x³y³-1/2x²y+y²-2x³y³+0.5x²y+y²+x³y³-2y-7
=(x³y³-2x³y³+x³y³)+(-1/2x²y+0.5x²y)+(y²+y²)-2y-7
=0+0+2y²-2y-7
=2y²-2y-7
结果中没有x
所以和x的值无关