# What is the vertex form of y=x^2-4x+9?

Apr 14, 2018

$y - 5 = {\left(x - 2\right)}^{2}$

#### Explanation:

The equation of the parabola is

$\text{ } y = {x}^{2} - 4 x + 9$

$\Rightarrow \text{ } y - 5 = {x}^{2} - 4 x + 4$

$\Rightarrow \text{ } y - 5 = {\left(x - 2\right)}^{2}$

So the parabola is of the form ${x}^{2} = 4 a y$ with the vertex at $\left(2 , 5\right)$.