In Example 1, change 12x to 20x.

Data from Example 1

Find the coordinates of the focus and the equation of the directrix and sketch the graph of the parabola y² = 12x. Because the equation of this parabola fits the form of Eq. (21.15), we know that the vertex is at the origin. The coefficient of 12 tells us that 4p = 12, p = 3 The focus is the point (3, 0), and the directrix is the line x = −3, as shown in Fig. 21.44.

x=-3]| T -8 -4 8 y 4 0 -4 -8 P>0; opens right F(3,0) 4 Fig. 21.44 8 00 X