(1/2xy+y平方+1)+(x平方-1/2xy-2y平方-1)等于多少,

问题描述:

(1/2xy+y平方+1)+(x平方-1/2xy-2y平方-1)等于多少,

(1/2xy+y平方+1)+(x平方-1/2xy-2y平方-1)
=1/2xy+y²+1+x²-1/2xy-2y²-1
=x²-y²