4.2 & 4.3 Systems of Equations (Sub & Elimination)

y = 6x - 11

-2x - 3y = -7

2x - 3y = -1

y = x - 1

Solve the following systems of equations using substitution:

y = 8

y = -4x + 4

• (8, -1)

• (-28, 8)

• (-1, 8)

• (8, -28)

Solve the following systems of equations using substitution:

y = 3 - x

3y + x = 5

• No solution

• (1, 2)

• (3, 0)

• (2, 1)

Solve:
y=8x+1
y=6x+3

• (1, 9)
• (4, 14)
• (0, 1)
• (2, 4)

Which is the best method to use?

y = 6x − 11

−2x − 3y = −7

• Graphing

• Substitution because a variable is isolated.

• Elimination because both equations are in standard form.

Solve the following systems of equations using substitution:

2y + x = -15

x = 3y

• (-3, -9)

• (-9, -3)

• (-3, 9)

• (9, -3)

Solve this system of equations. 
y = 2x + 1
y = 4x - 1

• (1,3)

• (-1,-3)

• (-1,3)

• (3,1)

Solve using elimination.

4x + 8y = 20

-4x + 2y = -30

• (-7,1)

• (2,-5)

• (-2,5)

• (7,-1)

Now, our equations will look like this

-4x - 6y = -24

4x - 7y = - 54

Let's combine (add) these 2 equations to ELIMINATE the x variable. What would our combined equations be?

• -1y = 30

• 13y = -30

• -1y = -78

• -13y = -78