2x-y-(2y平方-x平方)-5x+y+(x平方+2y平方),x=-1,y=1

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2x-y-(2y平方-x平方)-5x+y+(x平方+2y平方),x=-1,y=1

2x-y-(2y平方-x平方)-5x+y+(x平方+2y平方),x=-1,y=1
2x-y-(2y平方-x平方)-5x+y+(x平方+2y平方),x=-1,y=1

2x-y-(2y平方-x平方)-5x+y+(x平方+2y平方),x=-1,y=1
2x-y-(2y^2-x^2)-5x+y+(x^2+2y^2)
=2x-y-2y^2+x^2-5x+y+x^2+2y^2
=2x^2-3x
=2+3
=5

2x-y-(2y²-x²)-5x+y+(x²+2y²)
=2x-y-2y²+x²-5x+y+x²+2y²
=2x²-3x
当x=-1,y=1
x²-3x=2+3=5