若|x-7|+|y+6|=0,求x+y的值.怎么算?

若x+y=6,xy=2.75,x-y>0,求x-y的值 若x*x+y*y-8x+6y+25=0,求y的x次方 若x^2+y^2-10x-6y+34=0,求（x-y)/(x+y)的值 若x、y满足2x+y=6,x-3y=1,求7y(x-3y)²-2(3y-x)³的值 求f(x,y)=x+y+7的最大值,使(x,y)满足x+2y≤10,2x+y≥6,y≥0 已知x+y=6,xy=7,试求x*x+y*y,x*x-y*y的值 x*x+2x-y*y+6y-8=0,x+y不等于2,求x-y的值 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*y)的值 若（x+y+1）的平方+|x-y+2|=0,求代数式3（x+y）的平方-7（x-y）-9（x+y）的平方-6（x-y）的值 已知x.x+y.y-6x-8y+25=0,求3x.x+5y的值 若(x+y)(x+y-1)-2=0,求x+y的值求 若(x-2)的平方+15y-11=0,求代数式-3(2x-y)-{7x-[6x+2y-(10x-8y)]-x-2(3x-4y)}的值 已知x的平方+y的平方-8x+6y+25=0,求(x-y+4xy/x-y)(x+y-4xy/x+y) 若｜y+5｜+(5x+1)2=0,求-3(2x-y)-｛7x-[6x+2y-(10x-8y)]-x-2(3x-4y)｝的值 若|y+5|+(5x+1)^2=0,求代数式-3(2x-y)-{7x-[6x+2y-(10x-8y)]-x-2(3x-4y)}的值 若｜y+5｜+(5x+1)^2=0,求-3(2x-y)-｛7x-[6x+2y-(10x-8y)]-x-2(3x-4y)｝的值 若X^2+y^2+2x-6y+10=0,求y^2x-x^2011的值 若|x-7|+|y+6|=0,求x+y的值.怎么算?