# What is the y intercept for a line with point (9,-5) slope -1?

Sep 29, 2015

The y intercept = 4

#### Explanation:

The general equation for a straight line is:

$y = m x + c$

$m$ is the gradient

$c$ is the intercept which is the point at $x = 0$ where the line cuts the $y$ axis.

From the co-ordinates given we can say that:

$x = 9$

$y = - 5$

Putting these values into the general equation gives:

$- 5 = \left(- 1 \times 9\right) + c$

$9 - 5 = c$

$c = 4$

Which is the $y$ intercept.

This means the equation of the line is:

$y = - x + 4$

It looks like this:

graph{y=-x+4 [-2.44, 7.56, -0.32, 4.68]}

You can see how the line cuts the y axis at $y = 4$