Intro to Elimination

Solve the following system of equations using the elimination method:

3x - 2y = 8

5x + 4y = 6

• x = -2

  y = -6

• x = 5

  y = 4

• x = 2

  y = -1

• x = 3

  y = -2

Solve the following system of equations using the elimination method:

2x + 5y = 9

3x - 5y = 1

• x = -8

  y = -5

• x = -8

  y = 5

• x = 2

  y = 1

• x = 1

  y = 2

Solve the following system of equations using the elimination method:

4x - 3y = 5

2x + 3y = 1

• x = 1

  y = 1/3

• x = -1

  y = -1/3

• x = 1

  y = -1/3

• x = 0

  y = 0

Solve the following system of equations using the elimination method:

3x + 2y = 9

3x - 3y = 4

• x = 11/3

  y = 1

• x = 7/3

  y = 1

• no solution

• x = 35/3

  y = -13

Solve the following system of equations:

3x - 4y = 12

6x - 8y = 16

• x = 13/2

  y = -15/8

• x = 5/2

  y = -9/8

• x = 8

  y = 3

• No Solution

Solve by elimination:

4x + 9y = 28

-4x - y = -28

• (-7,0)

• (6,0)

• (-6,0)

• (7,0)

What variable do you eliminate?

4x + 8y = 20

−4x + 2y = −30

• X because they have opposite signs

• Y because they have opposite signs

What can we do so that they match?

• Let's subtract so that we can get matching numbers!

• Let's multiply #2 by 2 to match #1!

• Let's add so we can get matching numbers!

If we multiply Equation #2 by 2, how does it change?

• 7x - 6y = 14

• 10x - 8y = 24

• 5x - 4y = 12

What variable do you eliminate?

4x + 8y = 20

−4x + 2y = −30

• X because they are matching and have opposite signs

• Y because they are matching and have opposite signs