Systems of Equations

Solve the system by graphing. **Use scrap paper or graph in your calculator
y=-x-2
y=1/2x+1

• (6, 4)
• (-2, 0)
• (2, 0)
• (0, -2)

How can you use the substitution method to solve this system?
2x+7=y
4x+y=7

• Plug in 2x+7 in for 7 in second equation
• plug 2x+7 in for y in the second equation
• plug 4x+y in for y in the first equation
• set 2x+7 = 4x+y

2x+7=y
4x+y=7
Now we have 4x + 2x+7 = 7 as our new equation. Solve for x.

• x=7
• x=7/13
• x=14/6
• x=0

2x+7=y
4x+y=7
Now we know x=0. What is y?

• y=7/4
• y=0
• y=7
• y=-7/2

Is (2,-1) a solution to the system:
2x-4y=8
y=-3x+6

• Yes; it makes both equations true
• No; it makes the first equation true but not the second
• no; it makes the second equation true but not the first
• no; it makes both equations false

Find f(3)

• 3
• 4
• 0
• undefined

How do you solve this system by substitution?
y=-3x+5
5x-4y=-3

• plug in -3x+5 in for x in second equation
• plug in -3x+5 in for y in second equation
• plug in 5x-4y in for y in the first equation

What property do you use in the next step to solve this equation?
5x-4(-3x+5)=-3

• commutative property
• associative property
• distributive property
• property of equality 

What can you multiply the second equation by to get the y terms to cancel?
-3x-8y=20
-5x+y=19

• 3
• 5
• -8
• 8