Question

A car’s headlight contains a parabolic reflector. A special bulb with two filaments is used to produce the high and low beams. The filament placed at the focus produces the high beam and the filament placed off-focus produces the low beam. The equation of the reflector is y=1/12 x^2. How far from the vertex should the filament for the high beam be placed? The x and y values are in centimeters. Be sure to include the correct unit in your answer.

what equation should I use