怎样化简x²+y²+4x-6y+13

已知x,y满足x²+y²-4x+6y+13=0则(3x+y)²-(3x+y)(3x-y)的 1.化简求值：(x+y)(x-y)-(x-y)²-6x²y÷2y+(2xy)²÷(-4xy 化简求值(x+y)(x-y)-(x-y)²-6x²y/2y+(2xy)²/(-4xy)其中 化简求值(x+y)(x-y)-(x-y)²-6x²y除2y+(2xy)²除(-4xy)其中 化简 3(X-Y)²-4(X-Y)+7(X-Y)-6(X-Y)² (x+y)(x-2y)(x²-4y²) 其中x=8 y=-8 化简求值 已知x²+4y²-6x+8y+13=0,求x-y/x+y的值. 已知x²+y²+13-4x+6y=0,求（2x-y)²-2(2x-y)(x+2y)+(x+ 已知实数x、y满足x²+y²+4x-6y+13=0 x²-4x+y²+6y+13=0,x-y=? x²-4x+y²+6y+13=0.x=?y=? 化简求值：(x+y)(x-y)+(x-y)²-(6x²y-2xy²)÷2y,其中x=-2,