9x²-y² =48 x+y=6 求x,y的值

已知x²-y²=12,x+y=6,求x,y的值 已知x²+4y²-6x+8y+13=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 已知非零有理数x,y满足x²-4xy+4y²=0,求x-y/x+y-y-x/x+y的值. 若|x+y-1|+（x-y-2)²=0,求代数式（x+2y)(x-2y）-（2x-y)(-y-2x)的值. (1)已知x+y=6,x²-y²=5,求x-y的值（2）若x+y=3,x²+y² 已知x、y是实数,且x²+y²-4x-6y+12=0.求x²+y²的最值,x-y 若x-y=6,xy=-8,求代数式(x+y+z)²+(x-y-z)(x-y+z)-2·z(x+y)的值 已知x,y的值满足方程组x+2y=3,x-y=-2,求x/(x-y)²+x²-y²/(x+ 已知x²+y²-2xy-6x+6y+9=0,求x+y的值 已知x²+y-2xy-6x+6y+9=0,求x-y的值 x/y=3,求x²+y²-xy/x²-y²的值.