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问题: 圆x2+(y+1)2=a(a>0)与直线x+y-2=0有公共点,求实数a的取值范围。过程请尽量详细!

圆x2+(y+1)2=a(a>0)与直线x+y-2=0有公共点,求实数a的取值范围。过程请尽量详细!急急急!

解答:

x^2+(y+1)^2=a(a>0)
x+y-2=0-->y+1=3-x
x^2+9-6x+x^-a=0
2x^2-6x+9-a=0
圆x2+(y+1)2=a(a>0)与直线x+y-2=0有公共点
判别式》=0
36-72+8a>=0
8a>=36
a>=4.5