Simultaneous Equations

Compare the two equations.  What can we do to eliminate one of the variables? 

Flip the second equation and compare the equations again.

Add the equations

 2x + y = 5

-x - y = -1

x  = 4

Substitute x into 2x + y = 5

2(4) + y = 5

8 + y = 5

y = -3

Compare the two equations.  What can we do to eliminate one of the variables? 

Flip the second equation and compare the equations again.

Add the equations

 2x + y = 1

 -x  - y  = 2

  x = 3

Substitute x into 2x + y = 1

2(3) + y = 1

6 + y = 1

y = -5

Compare the two equations.  What can we do to eliminate one of the variables? 

Flip the second equation

Add the equations

 2x - y = 1

-x + y = 2

x           = 3

Substitute x into 2x - y = 1

2(3) - y = 1

6 - y = 1

y = 5