4: Systems of Equations by Elimination

What is a solution to a system of linear equations?

• The point where both lines intersect

• The point where the y-axis and x-axis meet

• An ordered pair that both lines share

• A salt dissolved in water

Tags

CCSS.8.EE.C.8A

The coefficients of the eliminated variable must be _____.

• the same number opposite signs (opposites)

• exactly the same

• completely different

• doesn't matter

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

4x +  8y = 20
-4x + 2y = -30
Which variable will be eliminated?

• The  x
• The  y
• The  z
• The unknown

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

What would be the first step in finding the solution with elimination?

4x + 3y = 1

x - 3y = -11

• Add to eliminate the 3y and -3y

• Add to eliminate the 4x and x

• change all the signs of the second equation

• add 1 and -11

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

To add and eliminate the x’s to solve, what value should you multiply the top equation by.

2x - 5y = 10.

4x + 15y = -10

• -2

• 2

• 3

• -3

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

what number should you multiply the top equation to eliminate variable x by adding:

5x - 2y = 11

-10x + 3y = -4

• 5

• -1

• 2

• -2

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

What variable do you eliminate?

4x + 8y = 20

−4x + 2y = −30

• X because they have opposite signs

• Y because they have opposite signs

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

• 5

• 0

• -1

• 2

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

x + 2y = -4
x - 2y = 8

• (2,5)

• (2,-3)

• (2,-2)

• (-3,2)

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