How To Graph A Parabola Y X 5 2 3 Socratic So, the equation will be x 2 = 4ay Substituting (3, 4) in the above equation, (3) 2 = 4a(4) 9 = 16a a = 9/16 Hence, the equation of the parabola is x 2 = 4(9/16)y Or 4x 2 = 9y Go through the practice questions given below to get a thorough understanding of the different cases of parabolas explained above Practice Problems 1 Finding the yintercept of a parabola can be tricky Although the yintercept is hidden, it does exist Use the equation of the function to find the yintercept y = 12x 2 48x 49 The yintercept has two parts the xvalue and the yvalue Note that the xvalue is always zero So, plug in zero for x and solve for y y = 12(0) 2 48(0) 49 (Replace x with 0) y = 12 * 0 0 49 Y x 2 parabola