Systems of Equations Elimination

I can combine 2 linear equations if the coefficients are not opposites.

• True

• False

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve by elimination:

3x+7y=23

-3x-7y=-17

• No solution

• ARN

• (-3,3)

• (3,3)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve using elimination.

4x + 8y = 20

-4x + 2y = -30

• (-7,1)

• (2,-5)

• (-2,5)

• (7,-1)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Let's multiply the top equation by -2. What would be our new equation?

2x + 3y = 12

4x - 7y = - 54

• 4x - 6y = -24

• -4x - 6y = 12

• -4x - 6y = 24

• -4x - 6y = -24

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Now, our equations will look like this

-4x - 6y = -24

4x - 7y = - 54

Let's combine (add) these 2 equations to ELIMINATE the x variable. What would our combined equations be?

• -1y = 30

• 13y = -30

• -1y = -78

• -13y = -78

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Let's solve for y.

-13y = -78

• y = 6

• y = 1

• y = 8

• y = 30

Tags

CCSS.6.EE.B.7

Now, let's find the solution to the system.

2x + 3y = 12

4x - 7y = - 54

• (-3, 2)

• (-3, -2)

• (6, -3)

• (-3, 6)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Your Turn:

Solve by elimination

2x + 9y = -7

6x - 3y = 9

• (-1, -1)

• (2,-1)

• (1,1)

• (1,-1)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve by elimination 
-2x + 6y = 16
-4x  - 3y = 2

• (2,2)
• (-2, -2) 
• (-2,2)
• (2,1)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve the system of Equation (x,y)
3x + 2y = –13
3x + 4y = 1 

• (-9,7)
• (7,-9)
• (4,-7)
• (-7,-4)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6