Since circle passes through the origin & diameter along the x-axis therefore its centre is (a,0) and its eq. is (x-a)
2+y
2=a
2or x
2+y
2-2ax=0.............1
equation of the circle passing through the circle(1) & y=mx
x2+y2-2ax+c(y-mx)=0 where c is any constant its center is(a+m/2,-c/2)
center lies on y=mx
-c/2=m(a+m/2)
putting the value of c in eq be get the required answer.
Thanks & Regards
Sunil Raikwar