Crystal G. answered • 10/14/12
Bilingual Math/Spanish Ivy League Tutor o' Awesomeness
It depends on what kind of information you are given, and what kind of parabola (vertical or horizontal) you have.
If you have a vertical parabola you can get it to be in the the form (x - h)2 = 4p(y - k) by completing the square. Then the vertex is (h, k) and the focus is (h, k + p). Since it's a vertical parabola, we change the y-coordinate of the vertex.
If you have a horizontal parabola, of the form (y - k)2 = 4p(x - h), vertex is (h, k) so focus is (h + p, k). (Since parabola is horizontal, the focus is related to the x-coordinate of the vertex.)
That's a super general answer, but I hope it helps for now.
