# What is the vertex of the parabola y=4x-x^2?

Mar 17, 2016

Vertex is $\left(- 2 , - 4\right)$

#### Explanation:

Given -

$y = 4 x - {x}^{2}$

We shall rewrite it as -

$y = {x}^{2} + 4 x$

X- co-ordinate of the vertex is -

$x = \frac{- b}{2 a} = - \frac{4}{2} = - 2$

Y - co-ordinate at $x = - 2$

$y = {\left(- 2\right)}^{2} + 4 \left(- 2\right)$
$y = 4 - 8 = - 4$

Its vertex is -

$\left(- 2 , - 4\right)$