1.xy=6,x²+y²=12,x与y相等吗?

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1.xy=6,x²+y²=12,x与y相等吗?
2.x+y=6,xy=z²+9,求x,y,z的值.
3.若a-b=8,ab+c²+16=0,求证a+b+c=0.
4.若x²+2x+y²-8y+17=0,求x,y的值.

1.相等y=6/x x^2+(6/x)^2=12 解得x^2=6,y^2=6 xy=6 x=y
2.x=3 y=3 z=0 x=6-y
(6-y)y=z^2+9
6y-y^2=z^2+9
y^2-6y+9+z^2=0
(y-3)^2+z^2=0
y=3,z=0
x=3
3.a=b+8
(b+8)b+c^2+16=0
b^2+8b+16+c^2=0
(b+4)^2+c^2=0
b=-4 c=0 a=4
a+b+c=0
4.x^2+2x+1+y^2-8y+16=0
(x+1)^2+(y-4)^2=0
x=-1 y=4

1.xy=6,x²+y²=12,x与y相等吗? 已知x²+y²-8x+6y+25=0,求（x-y+4xy/x-y）（x+y-4xy/x+y） x/xy-y²与y/x²-xy 通分 1.x-y=16,xy=6,求3x²y-6xy²+18y+6 1.设A=2x²-3xy+y²-x+2y,B=4x²-6xy+2y²-3x-y, 1.设A=2x²-3xy+y²+x-3y,B=4x²-6xy+2y²+4x-y, 已知x²-xy,xy-y²=－12,分别求式子x²-y²与x²-2xy 已知x/y=2,求x²-xy+3y²/x²+xy+6y²的值已知x+y=0.2,x+3y=1.求3X²+12XY+12Y² 已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y² 已知(x+y)²=1 (x-y)²=49,求x²+y²与xy的值 (x+y)²=1,(x－y)²=49,求x²+y²与xy的值