Systems of Equations
Use substitution or elimination to find where two lines meet.
The rules
- Elimination: line up the equations and add or subtract to cancel one variable.
- Substitution: solve one equation for a variable and plug it into the other.
- Parallel lines have no solution. Identical lines have infinitely many.
- Always find both variables, then check in both equations.
Watch out: Stopping after finding only x.
Worked example
If x + y = 10 and x − y = 4, what is y?
- Add: 2x = 14, so x = 7.
- Then y = 10 − 7 = 3.
Answer: 3
Try it yourself
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