SOLUTION: Write an equation in slope-intercept form of the line joining the points A(-10, 50) and B (10, -30)

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Question 316319: Write an equation in slope-intercept form of the line joining the points A(-10, 50) and B (10, -30)
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

First let's find the slope of the line through the points and


Note: is the first point . So this means that x%5B1%5D=-10 and y%5B1%5D=50.
Also, is the second point . So this means that x%5B2%5D=10 and y%5B2%5D=-30.


m=%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29 Start with the slope formula.


m=%28-30-50%29%2F%2810--10%29 Plug in y%5B2%5D=-30, y%5B1%5D=50, x%5B2%5D=10, and x%5B1%5D=-10


m=%28-80%29%2F%2810--10%29 Subtract 50 from -30 to get -80


m=%28-80%29%2F%2820%29 Subtract -10 from 10 to get 20


m=-4 Reduce


So the slope of the line that goes through the points and is m=-4


Now let's use the point slope formula:


y-y%5B1%5D=m%28x-x%5B1%5D%29 Start with the point slope formula


y-50=-4%28x--10%29 Plug in m=-4, x%5B1%5D=-10, and y%5B1%5D=50


y-50=-4%28x%2B10%29 Rewrite x--10 as x%2B10


y-50=-4x%2B-4%2810%29 Distribute


y-50=-4x-40 Multiply


y=-4x-40%2B50 Add 50 to both sides.


y=-4x%2B10 Combine like terms.


So the equation that goes through the points and is y=-4x%2B10