Question 1040661:  Find the equation of the circle if a triangle whose sides lie on the lines 3x+4y=8, 3x-4y=32 and x-8=0 inscribed the circle.  
 Answer by Fombitz(32388)      (Show Source): 
You can  put this solution on YOUR website! Find the intersection points. 
From eq. 3, 
  
Substituting into eq. 1, 
  
  
  
  
(8,-4) 
Substituting into eq. 2, 
  
  
  
  
(8,-2) 
Finally adding eq. 1 and eq. 2, 
  
  
  
  
So, 
  
  
  
  
(20/3,-3) 
Now you have three points on the circle, solve for the circle. 
Use the general form, 
  
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(8,-4): 
  
  
4.  
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. 
(8,-2): 
  
  
5.  
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. 
(20/3,-3): 
  
  
  
6.  
Subtracting eq. 5 from eq. 4, 
  
  
  
Substituting into eq. 4, 
  
7.  
Substituting into eq. 6, 
  
8.  
Multiply eq. 7 by -9 and add to eq. 8, 
  
  
  
and substituting into eq. 7, 
  
  
  
  
. 
. 
  
You can complete the square to get into center-radius form, 
  
  
  
  
  
Center : ( , ) 
Radius :   
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