SOLUTION: if the line containing points (-8,m) and (2,1) is parallel to the line containing points (11,-1) and (7,m+1), what must be the value of m?

Algebra ->  Coordinate Systems and Linear Equations  -> Lessons -> SOLUTION: if the line containing points (-8,m) and (2,1) is parallel to the line containing points (11,-1) and (7,m+1), what must be the value of m?      Log On


   

Question 150713: if the line containing points (-8,m) and (2,1) is parallel to the line containing points (11,-1) and (7,m+1), what must be the value of m?
Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
In order to two lines to be paralle, they need to have the same slope. Generally slope is assigned to a variable named "m". In this problem the points are using m in them, so use a different variable for slope.
slope using the first two points
s+=+%28y%5B2%5D+-+y%5B1%5D%29%2F%28x%5B2%5D+-+x%5B1%5D%29
s+=+%281-m%29%2F%282+-+%28-8%29%29
s+=+%281-m%29%2F10


slope using the second two points
s+=+%28y%5B2%5D+-+y%5B1%5D%29%2F%28x%5B2%5D+-+x%5B1%5D%29
s+=+%28m%2B1+-+1+%29%2F%287+-+11%29
s+=+m%2F%28-4%29

Now set the two slopes equal
%281-m%29%2F10+=+-m%2F4
1-m+=+-5m%2F2
2+-+2m+=+-5m
2+=+-3m
-2%2F3+=+m