Question

求圆心在直线4x+y=0上,且与直线x+y-1=0相切于点M(3,-2)的圆的方程

Answer 1

圆心C

L:x+y-1=0

k(L)=-1

k(MC)=1

直线MC:x-y-5=0.(1)

圆心在:4x+y=0.(2)

(1)+(2):

x=1,y=-4

r^2=(1-3)^2+(-4+2)^2=8

圆的方程:(x-1)^2+(y+4)^2=8