1. Solving Systems of Equations by Elimination
Teacher Twins©2014

2. Warm Up (4, -1) (8, -1) (5, -8) Solve each system by substitution.
4x + 5y = 11
y = 3x – 13
x = -2y + 6
6x – 8y = 56
y = -4x + 12
y = -2x + 2
(4, -1)
(8, -1)
(5, -8)

3. Solving Systems of Equations by Elimination

4. Elimination Using
Addition

5. Solve the system by elimination. 5x + 3y = 12 -4x – 3y = 24
To do elimination you must have opposites. In this problem the 3y and -3y are opposites.
x = 36
x = 36
Add the equations together.
5x + 3y = 12
5(36) + 3y = 12
y = 12
y = -56
Find the y value by using one of the equations.
Answer – ( 36, -56)

6. Try on your own.
-4x + 3y = -3
4x – 5y = 5
(0, -1)

7. Solve the system by elimination. 7x + 3y = -6 7x – 2y = -31
To do elimination you must have opposites. In this problem the 7x and 7x are not opposites. You must make them opposites by multiplying one of the equations by -1 (or subtracting the equations).
7x + 3y = -6
-7x + 2y = 31
Multiplied by -1
y = 25
y = 5
Find the x value by using one of the equations.
7x + 3y = -6
7x + 3(5) = -6
x = -3
Answer – (-3, 5)

8. Try on your own
6x – 3y = 27
2x – 3y = 11
(4, -1)

9. Closure (-3, 1) Solve the system by elimination. -4x + 5y = 17