SOLUTION: How do you know when an equation has infinetly many solutions, and when an equation has no solution?

Algebra ->  Equations -> SOLUTION: How do you know when an equation has infinetly many solutions, and when an equation has no solution?      Log On


   



Question 362348: How do you know when an equation has infinetly many solutions, and when an equation has no solution?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
When your equations lead to an inconsistency, such as, 1=0 or similar, then you have two parallel lines with no solution.
Example:
1.2x%2By=12
2.2x%2By=5
Subtract eq. 2 from eq. 1,
2x%2By-2x-y=12-5
0=7
No solution, the lines are parallel.
.
.
.
When your equations lead to an identity, such as, 5=5 or similar, then you have two lines that are the same line and have infinitely many solutions.
1.2x%2By=6
2.4x%2B2y=12
Multiply eq. 1 by -2 and add to eq. 1,
-4x-2y%2B4x%2B2y=-12%2B12
0=0
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).