# What is the vertex form of  f(x) = -5x^2-2x+9 ?

Feb 12, 2018

Vertex is $\left(- 0.2 , 9.2\right)$ and vertex form of equation is $f \left(x\right) = - 5 {\left(x + 0.2\right)}^{2} + 9.2$

#### Explanation:

$f \left(x\right) = - 5 {x}^{2} - 2 x + 9 \mathmr{and} f \left(x\right) = - 5 \left({x}^{2} + 0.4 x\right) + 9$ or

$f \left(x\right) = - 5 \left({x}^{2} + 0.4 x + {\left(0.2\right)}^{2}\right) + 5 \cdot 0.04 + 9$ or

$f \left(x\right) = - 5 {\left(x + 0.2\right)}^{2} + 9.2$. Vertex is $\left(- 0.2 , 9.2\right)$ and

vertex form of equation is $f \left(x\right) = - 5 {\left(x + 0.2\right)}^{2} + 9.2$ [Ans]