Elimination Method

In class on Thursday, we reviewed the three ways to solve systems we knew; graphing, setting equal, and substitution. Then we learned the 4th method, Elimination.

For example,

4x+5y=47
8x+2y=38
You would multiply the first equation by 2
2(4x+5y=47)
8x+10y=94
Then you would subtract the second equation from the first, cancelling out the x
8x+10y=94
- 8x+2y=38
8y=56
y=7

Then you would substitute in 4 for x
4x+5(7)=47
4x+35=47
4x=12
x=3
The answer to the system is (3,7).
TIPS
You can solve for either the x or the y.
Sometimes you may have to multiply both equations to be able to cancel out a variable.
You can add or subtract the equations to get an answer.