# How do you write the equation in point slope form given (2, 5) and (–1, 8)?

Jul 29, 2017

See a solution process below:

#### Explanation:

First, we need to determine the slope of the line. The slope can be found by using the formula: $m = \frac{\textcolor{red}{{y}_{2}} - \textcolor{b l u e}{{y}_{1}}}{\textcolor{red}{{x}_{2}} - \textcolor{b l u e}{{x}_{1}}}$

Where $m$ is the slope and ($\textcolor{b l u e}{{x}_{1} , {y}_{1}}$) and ($\textcolor{red}{{x}_{2} , {y}_{2}}$) are the two points on the line.

Substituting the values from the points in the problem gives:

$m = \frac{\textcolor{red}{8} - \textcolor{b l u e}{5}}{\textcolor{red}{- 1} - \textcolor{b l u e}{2}} = \frac{3}{-} 3 = - 1$

The point-slope formula states: $\left(y - \textcolor{red}{{y}_{1}}\right) = \textcolor{b l u e}{m} \left(x - \textcolor{red}{{x}_{1}}\right)$

Where $\textcolor{b l u e}{m}$ is the slope and $\left(\textcolor{red}{{x}_{1} , {y}_{1}}\right)$ is a point the line passes through.

We can substitute the slope we calculated and the values from the first point in the problem giving:

$\left(y - \textcolor{red}{5}\right) = \textcolor{b l u e}{- 1} \left(x - \textcolor{red}{2}\right)$

We can also substitute the slope we calculated and the values from the second point in the problem giving:

$\left(y - \textcolor{red}{8}\right) = \textcolor{b l u e}{- 1} \left(x - \textcolor{red}{- 1}\right)$

$\left(y - \textcolor{red}{8}\right) = \textcolor{b l u e}{- 1} \left(x + \textcolor{red}{1}\right)$