(x+y)^2-6x^2+6y^2+9(x-y)^2的解

(x+y)^2-6x^2+6y^2+9(x-y)^2
=x^2+2xy+y^2-6x^2+6y^2+9x^2-18xy+9y^2
=4x^2-16xy+16y^2
=4(x^2-4xy+4y^2)
=4(x-2y)^2

(x+y)²-6x²+6y²+9(x-y)²
=(x+y)²-6(x²-y²)+9(x-y)²
=(x+y)²-6(x+y)(x-y)+9(x-y)²
=(x+y)²-2×3(x-y)×(x+y)+[3(x-y)]²
=[(x+y)-3(x-y)]²
=(-2x+4y)²
=4(x-2y)²

=x^2+y^2+2xy-6x^2+6y^2+9(x^2+y^2-2xy)
=x^2+2xy+y^2-6x^2+6y^2+9x^2-18xy+9y^2
=4x^2-16xy+16y^2
=4(x-2y)^2

原式=x²+2xy+y²-6x²+6y²+9x²-18xy+9y²
=4x²-16xy+16y²
=4（x²-4xy+4y²）
=4（x-2y）²

x=-10000 y=-5000
无视我吧