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)

Thanks in advanced.

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- Jan 4th 2008, 04:14 AMnugiboyUrgent 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)

Thanks in advanced. - Jan 4th 2008, 04:30 AMcolby2152
You have two points, so in essence you are just connecting the dots. Use the equation of the slope:

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

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

Plug that in slope-intercept form.

$\displaystyle y=mx+b$ 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

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

$\displaystyle b = -5$

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