A point P on the parabola y² = 20x is 9 units from the focus…

Step 1. The constant. $4a = 20$, so $a = 5$.

Step 2. The abscissa. $x_1 + a = 9$, so $x_1 = 4$.

Step 3. The ordinate. $y_1^2 = 20 \times 4 = 80$, so $y_1 = \pm\sqrt{80} \approx \pm 8.94$.

Step 4. The directrix. The distance from the directrix $x = -5$ is $4 + 5 = 9$, the same as the distance from the focus.