1. 7.4 Solve Linear Systems by Multiplying First
Also called
Elimination Method Or
Linear Combinations Method

2. Steps to Solve Systems by Elimination
Line up the variables
Multiply one equation to eliminate a variable
Substitute the value into the other equation to solve for the second variable
Check to be sure the numbers work in both equations

3. Solve the system: 𝟐𝒙 −𝒚=𝟑 𝟒𝒙+𝟑𝒚=𝟐𝟏
Lined up – ok
Multiply the 1st equation by 3 to eliminate y
Use x to find y
Check
6x – 3y = 9
4x + 3y = 21
10 x = 30
x = 3
2(3) – y = 3
6 – y = 3
-y = -3
y = 3
4(3) + 3(3) = 21
Solution: (3, 3)

4. Solve the system: 𝒙+𝟐𝒚=𝟏 𝟓𝒙−𝟒𝒚=−𝟐𝟑
Which variable do you want to eliminate?

5. Solve the system: 𝟑𝒙+𝟐𝒚=𝟏𝟎 𝟐𝒙+𝟓𝒚=𝟑

6. Your turn…
Solve the system: 𝟑𝒙+𝟓𝒚=𝟐𝟓 𝟐𝒙 −𝟔𝒚=𝟏𝟐

7. Click on the link:

8. Homework:
P 454
#3-29 odd (skip 23)
33, 37, 41