An ellipse has the equation x^2+5y^2=5

a line has the equation y=mx+c

(1) Show that if the line is a tangent to the ellipse then c^2=5m^2+1

(2) hence find the equation of the tangent parallel to the line x-2y+1=0

(note ^ symbol: is the to the power of)

If anyone could help, I would much appreciate it. Thankyou