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December 18, 2014

December 18, 2014

Posted by **lisa** on Thursday, December 4, 2008 at 8:43pm.

slope:2/5 x-int=4.5

i knwo hwo to do it with y-int

but hwo doyou do it with x- int?

- math -
**DanH**, Thursday, December 4, 2008 at 9:19pmy = mx + b, and you're right, we do not know the y-intercept here.

so, y = (2/5)x + b.

They tell us the X-intercept is 4.5. How does this help us? The x-intercept is where it crosses the x-axis. At that point, y = 0. So, the line crosses the point (4.5,0).

So, now we substitute in 0 for y and 4.5 for x:

0 = (2/5)(4.5) + b.

We can solve for b, and we get

b= -9/5.

So, we now have our y-intercept, and use y = mx + b.

Does this make sense??

- math -
**lisa**, Thursday, December 4, 2008 at 9:21pmthank you =D

- math -
**DanH**, Thursday, December 4, 2008 at 9:25pmyou're welcome!

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