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Find the value of c such that the three points (5,5), (-3,1) and (6,c) lie on the same line.

Note: Three points are on the same line if the slope of the line through any two points is always the same.
 

 Apr 23, 2020
 #1
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First, let's find the equation of the line through  (5, 5)  and  (-3, 1).

  slope  =  (1 - 5) / (-3 - 5)  =  -4 / -8  =  ½

  equation:  y - 5  =  ½(x - 5)     --->     y  =  ½x + 2½

 

For the point  (6, c)   --->   c  =  ½(6) + 2½     --->     c  =  3 + 2½     --->     c  =  5½

 Apr 23, 2020

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