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

Jun 23, 2018

(2,4)

#### Explanation:

$\frac{- b}{2 a}$ gives the X coordinate of the vertex

$\frac{- 4}{2 \times - 1} = \frac{- 4}{- 2} = 2$

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

$y = 4 \times 2 - {2}^{2}$

$y = 8 - 4. \implies y = 4$