SOLUTION: Please help...I need to write an equation in slope-intercept form using the following coordinates (-1,-7) and (-8,-2). I got as far as finding the slope m=-5/7 but I'm confused wit

Algebra ->  Coordinate-system -> SOLUTION: Please help...I need to write an equation in slope-intercept form using the following coordinates (-1,-7) and (-8,-2). I got as far as finding the slope m=-5/7 but I'm confused wit      Log On


   

Question 84446: Please help...I need to write an equation in slope-intercept form using the following coordinates (-1,-7) and (-8,-2). I got as far as finding the slope m=-5/7 but I'm confused with rest of the equation. Thank you
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Use the form
m+=+%28y+-+y%5B1%5D%29+%2F+%28x+-+x%5B1%5D%29
and
m+=+%28y%5B2%5D+-+y%5B1%5D%29+%2F+%28x%5B2%5D+-+x%5B1%5D%29
where
P%5B1%5D = (x1 , y1)
P%5B2%5D = (x2 , y2)
(x1 , y1) = (-1 , -7)
(x2 , y2) = (-8 , -2)
m+=+%28-2+-+%28-7%29%29+%2F+%28-8+-+%28-1%29%29
m+=+%28-2+%2B+7%29+%2F+%28-8+%2B+1%29
m+=+-%285%2F7%29
now
m+=+%28y+-+y%5B1%5D%29+%2F+%28x+-+x%5B1%5D%29
-%285%2F7%29+=+%28y+-+%28-7%29%29+%2F+%28x+-+%28-1%29%29
-%285%2F7%29+=+%28y+%2B+7%29+%2F+%28x+%2B+1%29
multiply both sides by (x+1)
-%285%2F7%29%2A%28x+%2B+1%29+=+y+%2B+7
multiply both sides by 7
-5x+-+5+=+7y+%2B+49
7y+=+-5x+-+54
y+=+-%285%2F7%29x+-+54%2F7
check answer
Does line go through (-1 , -7) and (-8 , -2)?
y+=+-%285%2F7%29x+-+54%2F7
-7+=+-%285%2F7%29%2A%28-1%29+-+54%2F7
-7+=+5%2F7+-+54%2F7
-7+=+-%2849%2F7%29
-7+=+-7 OK
--------------------
y+=+-%285%2F7%29x+-+54%2F7
-2+=+-%285%2F7%29%2A%28-8%29+-+54%2F7
-2+=+40%2F7+-+54%2F7
-2+=+-%2814%2F7%29
-2+=+-2 OK