Day 3

• Objective: Students will be able to solve a system of equations by addition/subtraction.
• You can add or subtract the the equations to cancel out variables and make it easier to solve.  One equation goes on top of the other just like a regular addition or subtraction problem.  You work your way from left to right and subtract/add like terms to cancel either the y or x out.    

Quiz Time!!

1.) Solve the system using addition or subtraction:

     2x+3y=9

     2x-y=5

2.) Solve the system using addition or subtraction:

     -3x+y=0

     3x+2y=6

3.) Solve the system using addition or subtraction: 

     5x-2y=6

     3x+2y=2

Answers to Quiz:
1.) When you subtract the two equations, it cancels out the x's at first which makes it easier to solve for y.  Then when you find out what y is you can plug it back into the equation to find x.(see image below)






















2.) When you add the two equations together, it cancels out the x's at first which makes it easier to solve for y.  Then when you find out what y is you can plug it back into the equation to find x.(see image below)






















3.) When you add the two equations together, it cancels out the y's at first which makes it easier to solve for x.  Then when you find out what x is you can plug it back into the equation to find y.  (see image below)  

For more on how to solve a system of equations by adding/subtraction watch this: http://youtu.be/nTF6Kp_icFo