Find the equation of the circle whose center is on the straight line y = - 2x and passes through the origin bar and point a (2, - 1)

Find the equation of the circle whose center is on the straight line y = - 2x and passes through the origin bar and point a (2, - 1)

If the center of the circle is on the straight line y = - 2x, let the center of the circle (a, - 2A)
Let the circular equation: (x-a) &# 178; + (y + 2a) &# 178; = R & # 178;
Over (0,0), (2, - 1)
(0-a)²+(0+2a)²=r²
5a²=r²
(2-a)²+(-1+2a)²=r²
4-2a+a²+1-4a+4a²=r²
5a²-6a+5=r²
5a²-6a+5=5a²
6a=5
a=5/6
r²=5*(5/6)²=125/36
Circular equation: (X-5 / 6) &# 178; + (y + 5 / 3) &# 178; = 125 / 36