SOLUTION: what is the point-slope form of the linear equation whose graph passes through (-1,3) and (3,-9)

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Question 588315: what is the point-slope form of the linear equation whose graph passes through (-1,3) and (3,-9)
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=-1 and y%5B1%5D=3.
Also, is the second point . So this means that x%5B2%5D=3 and y%5B2%5D=-9.


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


m=%28-9-3%29%2F%283--1%29 Plug in y%5B2%5D=-9, y%5B1%5D=3, x%5B2%5D=3, and x%5B1%5D=-1


m=%28-12%29%2F%283--1%29 Subtract 3 from -9 to get -12


m=%28-12%29%2F%284%29 Subtract -1 from 3 to get 4


m=-3 Reduce


So the slope of the line that goes through the points and is m=-3


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-3=-3%28x--1%29 Plug in m=-3, x%5B1%5D=-1, and y%5B1%5D=3


y-3=-3%28x%2B1%29 Rewrite x--1 as x%2B1


So the answer is y-3=-3%28x%2B1%29

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