数学题目 在线等答案 对的 再加50

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

-(x^-2xy-y^)+(5x^-2xy-3y^)
=-x^+2xy+y^+5x^-2xy-3y^
=4x^+0-2y^
=4x^-2y^

2x^y-(5xy^-3x^y)-x^
=2x^y-5xy^+3x^y-x^
=5x^y-5xy^-x^
=5*1*1-5*1*1-1
=5-5-1
=-1

-(x^-2xy-y^）+（5x^,-2xy-3y^）
=-x²+2xy+y²+5x²-2xy-3y²
=4x²-2y²

2x^y-(5xy^-3x^y)-x^
=2x²y-5xy²-3x²y-x²
=-x²y-5xy²-x²
当x=-1,y=1时
原式=-1+5-1
=3

=6