化简
-(x^2-2xy-y^2）+（5x^2-2xy-3y^2）
=-x^2+2xy+y^2+5x^2-2xy-3y^2
=(-x^2+5x^2)+(2xy-2xy)+(y^2-3y^2)
=4x^2-2y^2
求值当x=-1,y=1时,求代数式2x^y-(5xy^-3x^y)-x^的值
2x^2y-(5xy^2-3x^2y)-x^2
=2x^2y-5xy^2+3x^2y-x^2
=(2x^2y+3x^2y)-5xy^2-x^2
=5x^2y-5xy^2-x^2
=5×(-1)^2×1-5×(-1)×1^2-(-1)^2
=5-(-5)-1
=9