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.

问题描述:

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.