### Vertex Form of Equation

The vertex form of a parabola's equation is generally expressed as: y = a(x-h)^{2}+k

- (h,k) is the vertex as you can see in the picture below
- If a is positive then the parabola opens upwards like a regular "U".
- If a is negative, then the graph opens downwards like an
**upside down**"U".

- If |a| < 1, the graph of the parabola widens. This just means that the "U" shape of parabola stretches out sideways. Explore the way that 'a' works using our interactive parabola grapher.
- If |a| > 1, the graph of the parabola becomes narrower(The effect is the opposite of |a| < 1).