Question 128667
YOU FIND THE FOCI & THE DIRECTRIC BY PLOTTING THE EQUATION THUS:
Y=(X^2/12)
{{{ graph( 300, 200, -16, 15, -10, 10, x^2/12 )}}} (graph 300x200 pixels, x from -16 to 15, y from -10 to 10, x^2/12).