即求以交点为直径的圆
将y=-2x-4代入圆:x^2+4x^2+16x+16+2x+8x+16-5=0
得:5x^2+26x+27=0
(5x+ 9)(x+3)=0
x=-9/5,-3
y=-2/5,2
中点为(-11/10,-1/2),
d^2=(-9/5+3)^2+(-2/5-2)^2=(6/5)^2+(12/5)^2=36/5,r^2=d^2/4=9/5
故所求圆为:(x+11/10)^2+(y+1/2)^2=9/5
即求以交点为直径的圆
将y=-2x-4代入圆:x^2+4x^2+16x+16+2x+8x+16-5=0
得:5x^2+26x+27=0
(5x+ 9)(x+3)=0
x=-9/5,-3
y=-2/5,2
中点为(-11/10,-1/2),
d^2=(-9/5+3)^2+(-2/5-2)^2=(6/5)^2+(12/5)^2=36/5,r^2=d^2/4=9/5
故所求圆为:(x+11/10)^2+(y+1/2)^2=9/5