Various forms of the parabola
| (x – h)2 = 4a(y – k) | (x – h)2 = – 4a(y – k) |
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| Focus = (h, a + k) | Focus = (h, k – a) |
| Eqn. of the directrix y – k + a = 0 | Eqn. of the directrix y – k – a = 0 |
| Axis of the parabola x – h = 0 | Axis of the parabola x – h = 0 |
| Vertex = (h, k) | Vertex = (h, k) |