1. Solving Systems of Equations by Elimination Day 2
Teacher Twins©2014
Systems

2. Warm Up (-2, 5) (6, -2) (0, 3) Solve each system. –x + y = 7 x + y = 3

3. Solving Systems of Equations by Elimination Day 2

4. Elimination Using
Multiplication

5. Solve the system by elimination. 2x + y = 23 3x + 2y = 37
Multiply first equation by -2.
To do elimination you must have opposites. In this problem you must make opposites. Look for the easiest way to make opposites.
-2( 2x + y = 23)
-4x + -2y = -46
-4x + -2y = -46
3x + 2y = 37
Add the equations. Using the new equation for the first equation.
-x = -9
x = 9
Find the y value by using one of the equations.
2(9) + y = 23
18 + y = 23
y = 5
Answer (9, 5)

6. Try on your own
2x – y = 4
7x + 3y = 27
(3, 2)

7. 4(-1) + 3y = 8 -4 + 3y = 8 Answer (-1, 4) y = 4
Solve the system by elimination.
4x + 3y = 8
3x – 5y = -23
You must multiply both equations to get opposites. Think of a common denominator. I will make the 3y and -5y , 15y and -15y.
5(4x + 3y = 8)
3(3x – 5y = -23)
20x + 15y = 40
9x – 15y = -69
Add the new equations.
29x + 0 = -29
x = - 1
4(-1) + 3y = 8
-4 + 3y = 8
y = 4
Use one of the original equations to find y.
Answer (-1, 4)

8. Try on your own
9x – 2y = -8
-7x + 3y = 12
(0, 4)

9. Closure
2x + 4y = 5
3x – 5y = 6
Which variable is the easiest to turn in to opposites? Why?
The y variable would be the easiest because it already has opposite signs.