∵|x+2y+1|+(2x-y-2)平方=0
∴x+2y+1=0
2x-y-2=0
∴x=3/5
y=-4/5
∴(2x-y)平方-2(2x+y)(2x-y)+(2x+y)平方
=[(2x-y)-(2x+y)]²
=4y²
=64/25