# Equation of a parabola

• Mar 24th 2009, 03:06 PM
Joanie
Equation of a parabola
I have to write the equation in standard form for the parabola with an axis of symmetry y=0 and focus (-5,0). I have no idea where to start with this one although I know the formula for the standard form of a parabola equation. I also know the focus and vertex are on the axis of symmetry. I do not know how to apply this information to the problem.

Thanks.(Speechless)
• Mar 24th 2009, 03:14 PM
rtblue
ok... an axis of symmetry is the X value of the vertex. Also the formula to find the axis of symmetry with a given quadratic equation(parabola) is -b/2a.

See where you can get with that :D
• Mar 24th 2009, 04:47 PM
stapel
Quote:

Originally Posted by Joanie
I do not know how to apply this information to the problem.

I don't believe the equation can be found with only the listed information, since we don't know on which side of the focus is the vertex, etc. I think we need one more piece of information.

(Note: The axis of symmetry provided the x-coordinate of the vertex only if that axis is vertical. This one is not.)