# Urgent graph question help needed

• Jan 4th 2008, 04:14 AM
nugiboy
Urgent graph question help needed
Hello

Im a bit stuck on this question:

Find the equation of line CD where -

C = (8,-3)
D = (4,-4)

Then show it meets the y axis at (0,-5)

• Jan 4th 2008, 04:30 AM
colby2152
Quote:

Originally Posted by nugiboy
Hello

Im a bit stuck on this question:

Find the equation of line CD where -

C = (8,-3)
D = (4,-4)

Then show it meets the y axis at (0,-5)

You have two points, so in essence you are just connecting the dots. Use the equation of the slope:

$slope = \frac{rise}{run} \Rightarrow m = \frac{y_1-y_2}{x_1-x_2}$

$m = \frac{1}{4}$

Plug that in slope-intercept form.

$y=mx+b$ where b is the y-intercept, it should end up being -5 in this case

Now, plug one of the coordinates in to find b

$-4=4\frac{1}{4}+b$

$b = -5$

$y = \frac{1}{4}x-5$