SOLUTION: Find the equation of a line that passes thru (3,7) and (2,-1)

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Question 172946: Find the equation of a line that passes thru (3,7) and (2,-1)
Found 2 solutions by jojo14344, josmiceli:
Answer by jojo14344(1513) About Me  (Show Source):
You can put this solution on YOUR website!

(3,7) and (2,-1)
First we get the Slope:
We solve via: m=%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29
m=%28-1-7%29%2F%282-3%29=-8%2F-1=8
Thru Points (3,7):
Via Point-Slope Form:
y=mx%2Bb ---->7=8%2A3%2Bb
b=7-24=-17
So, --->y=8x-17---->highlight%28-8x%2By%2B17=0%29, Standard Form
We see the graph:

Thank you,
Jojo

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Two points determine a line, so that's all you need
The general equation for a line is
y+=+mx+%2B+b
This looks like a single equation with 4 unknowns, and
that is unsolvable, but the 2 points given will allow
me to write 2 equations with 2 unknowns
given:
(3,7)
(2,-1)
(1) 7+=+m%2A3+%2B+b
(2) -1+=+m%2A2+%2B+b
Now I solve for m and b
First, subtract (2) from (1)
8+=+m
Now put this value for m back into (1)
7+=+8%2A3+%2B+b
b+=+7+-+24
b+=+-17
The equation of the line that passes trough (3,7) and (2,-1) is
y+=+8x+-+17
Now check the answer
(3,7)
7+=+8%2A3+-+17
7+=+24+-+17
7+=+7
OK
(2,-1)
-1+=+8%2A2+-+17
-1+=+16+-+17
-1+=+-1
OK