Solving System by Elimination & Substitution

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

8x + 14y = 4

-6x - 7y = -10

• (4, -2)

• (-2, 4)

• (0, 3)

• (-4, -2)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve using elimination. 
−4x − 4y = 0
4x + 4y = 0 

• (−6, −4) 
• Infinite number of solutions  
• (−6, 10) 
• (6, 4) 

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve by elimination 
-12x-10y= 0 
 6x+5y= -1

• infinite solutions
• (0,0)
• no solution 
• (2,1)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve by elimination

2x+9y= -7

6x-3y= 9

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

• Infinite number of solutions

• (0, 7)

• (-5, -7)

• (5, 7)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

x = 2

y = x - 2

What is the Solution?

• (2,0)

• (0,2)

• No Solution

• Many Solution

Tags

CCSS.8.EE.C.8B

y = -20

y = 2x - 8

• (20,6)

• (-6,20)

• (-6,-20)

• (6,-20)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

What is the first step in solving a system by Substitution?

• Make sure both equations are in standard form.
• Make sure at least one equation is solved for one variable.
• Make sure both equations are in slope-intercept form.
• Make sure both equations can be solved.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Which method would be best (quickest) for solving the system below:
x + y = 11
3x - 4y = -2

• Substitution
• Elimination
• Graphing
• None of these

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6