# What is the slope of the line passing through  (7,9) ; (-5,-9) ?

Jan 26, 2016

The slope is equal to $\frac{2}{3}$.

#### Explanation:

You can calculate the slope bij $\frac{\Delta y}{\Delta x} = \frac{{y}_{b} - {y}_{a}}{{x}_{b} - {x}_{a}}$.
Let's call the first point $B$ and the second one $A$, because $A = \left(- 5 , - 9\right)$ lays in the left half of the coördinate system, and $B = \left(7 , 9\right)$ in the right half.

Okay, ${y}_{b}$ is the $y$-coördinate of point $B$, so ${y}_{b} = 7$ etc.

Hold in mind that $1 - - 2$ is equal to $1 + 2 = 3$.
$\frac{\Delta y}{\Delta x} = \frac{{y}_{b} - {y}_{a}}{{x}_{b} - {x}_{a}} = \frac{7 - - 5}{9 - - 9} = \frac{7 + 5}{9 + 9} = \frac{12}{18} = \frac{2}{3}$.