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

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Answer 1 · 2015-09-29T22:22:41

The y intercept = 4

The general equation for a straight line is:

$y=mx+c$

$m$ 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:

$-5=(-1xx9)+c$

$9-5=c$

$c=4$

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 $y=4$