y=-mx+3
代入 ²+y²=x²+(-mx+3)²=(1+m²)x²-6mx+9
化简(1+m²)x²-6mx+9=6
(1+m²)x²-6mx+3=0
判别式36m²-12(1+m²)=0
2m²-1=0
m=±√2/2
当m=√2/2时
x=6m/(2(1+m²))=√2
y=2
当m=-√2/2时
x=-√2
y=2