Question

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

Answer 1

The slope is equal to `2/3`.

Explanation:

You can calculate the slope bij `(Delta y)/(Delta x) = (y_b-y_a)/(x_b-x_a)`.
Let's call the first point `B` and the second one `A`, because `A= (-5,-9)` lays in the left half of the coördinate system, and `B=(7,9)` 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`.
`(Delta y)/(Delta x) = (y_b-y_a)/(x_b-x_a) = (7--5)/(9--9)=(7+5)/(9+9)=12/18=2/3`.