# How do you evaluate sqrt(b^2-4ac) for a=-9, b=10, c=-1?

Jul 19, 2017

See a solution process below:

#### Explanation:

To evaluate this expression substitute:

$\textcolor{red}{- 9}$ for $\textcolor{red}{a}$

$\textcolor{b l u e}{10}$ for $\textcolor{b l u e}{b}$

$\textcolor{g r e e n}{- 1}$ for $\textcolor{g r e e n}{c}$

$\sqrt{{\textcolor{b l u e}{b}}^{2} - 4 \textcolor{red}{a} \textcolor{g r e e n}{c}}$ becomes:

$\sqrt{{\textcolor{b l u e}{10}}^{2} - \left(4 \cdot \textcolor{red}{- 9} \cdot \textcolor{g r e e n}{- 1}\right)} \implies$

$\sqrt{100 - 36} \implies$

$\sqrt{64} \implies$

$8$