# Question #b04b9

Aug 10, 2016

$y = - 5 x - 21$

#### Explanation:

Slope intercept form means $y = m c + c$ because in this form we can read off the slope (m) and the y-intercept directly.

We know the slope, but the point $\left(- 5.4\right)$ is not the y-intercept.
It would have to be $\left(0 , c\right)$

There are 2 methods:

Method 1 .: Substitute into $y = m x + c$ and find a value for $c$

$4 = \left(- 5\right) \left(- 5\right) + c$
$4 = 25 + c$
$- 21 = c$
Substitute for $m \mathmr{and} c$

The required form is $y = - 5 x - 21$

Method 2: Substitute into $y - {y}_{1} = m \left(x - {x}_{1}\right)$

$y - 4 = - 5 \left(x \textcolor{red}{- \left(- 5\right)}\right)$

$y \textcolor{b l u e}{- 4} = - 5 \left(x \textcolor{red}{+ 5}\right)$
$y = - 5 x - 25 \textcolor{b l u e}{+ 4}$