Equation of tangent for the parabola x2=4ay is
let tangent is drawn at (h,k) and it has a slope m
x2=4ay2x=4adydxdydx=2x4a=x2a(dydx)(h,k)=h2a=m⇒h=2amh2=4ak⇒k=4a2m24a=am2
Equation of tangent is
y−k=m(x−h)y−am2=m(x−2am)y−am2=mx−2am2y=mx−am2
So option A is correct.