Question 362348:  How do you know when an equation has infinetly many solutions, and when an equation has no solution? 
 Answer by Fombitz(32388)      (Show Source): 
You can  put this solution on YOUR website! When your equations lead to an inconsistency, such as,   or similar, then you have two parallel lines with no solution. 
Example: 
1.  
2.  
Subtract eq. 2 from eq. 1, 
  
   
No solution, the lines are parallel. 
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When your equations lead to an identity, such as,   or similar, then you have two lines that are the same line and have infinitely many solutions. 
1.  
2.  
Multiply eq. 1 by -2 and add to eq. 1, 
  
  
The lines are the same line (eq. 2 is 2 times eq. 1), there are infinitely many solutions (every solution of eq. 1 is also a solution of eq. 2). 
 
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