Substitution

Solve this system of equations by substitution:

y = -1x - 5

4x - 8y = 4

• 4x - 8(-1x - 5) = 4

• 4(-1x - 5) - 8y = 4

• 4x - 8 = -1x - 5

• -1x - 5 = -8

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

What is the SECOND STEP in solving this system by substitution?

y = -1x - 5

4x - 8y = 4

First step: 4x - 8(-1x - 5) = 4

• 4x - 8x - 40 = 4

• 4x + 8x + 40 = 4

• 4x + 8x - 40 = 4

• 4x - 8x + 40 = 4

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve:
y = 7x + 9
2y + 2x = -18

• (5, 0)
• (9, 18)
• (-2, -5)
• (1, 16)

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

What is the SECOND STEP in solving this system.

x= 7 - 2y

2x + y = 5

FIRST STEP: 2(7 - 2y) + y = 5

• 14 - 2y + y = 5

• 14 - 4y + y = 5

• 14 + 4y + y = 5

• 14 + 2y + y = 5

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

What is the first step to solving this system of equations by substitution?

x = -3y - 17

2x + 3y = -7

• 2(-3x - 17) + 3x = -7

• 2x + 3(-3x - 17) = -7

• 2(-3y - 17) + 3y = -7

• 2(3y + 17) + 3y = -7

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

What is the first step to solving this system of equations by substitution?

y=8x+1

y=6x+3

• y = 6(8x + 1)

• -8x - 1 = 6x + 3

• x = 8(6x + 3)

• 8x + 1 = 6x + 3

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

What is the first step to solving this system by substitution?

y = 4x - 10

y = 3x - 5

• y = 4(3y - 5) - 10

• y = 3(4x - 10) - 5

• 4x - 10 = 3x - 5

• y = y

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

What is the first step to solving this system by substitution?

y= 4x + 3

2x - 3y = 21

• 2x - 3y = 4x + 3

• 2x - 3(4x + 3) = 21

• 2(4x + 3) - 3y = 21

• 2x - 3 = 4x + 3

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

^{What is the solution?} 

• 1
• -2
• (1, 2)
• (1, -1)

Tags

CCSS.8.EE.C.8B

How many solutions does the graph have?

• One solution

• No solution

• Infinite solutions

Tags

CCSS.8.EE.C.8A