Solve System of Equations Using Elimination and Substitution

Solve the system of equations using substitution

y = -6

-3x - 6y = 24

• (6, 6)

• (6, -6)

• (4, -6)

• (-6, 4)

What is the solution?

• (1, -1)

• (-1, 1)

• (0, -2)

• (2, 0)

Solve for x and y
y = 2x + 1
y = 4x - 1

• (1,3)

• (-1,-3)

• (-1,3)

• (3,1)

Solve the system given:
3x - y = 7
2x + y = 3

• (-1,2)

• (5,4)

• (4,5)

• (2,-1)

Which answer has a correct first step for this system:

• The variable is already isolated, so we've already solved the system.

• The variable is already isolated for y, so we substitute it in the first equation and solve for x

  3x + 3(3x + 5) = 3

• Free sha vaca doo

• The variable is already isolated for y, so we substitute it in the second equation and solve for x

  y = 3(3x + 3y) = 3

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.

What variable do you eliminate?

4x + 8y = 20

−4x + 2y = −30

• X because they have opposite signs

• Y because they have opposite signs

Solve using elimination. 
 4x + 8y = 20
-4x + 2y = -30

• (-7,1)

• (2,-5)

• (-2,5)

• (7,-1)

Solve by elimination:
4x+9y=28
-4x-y=-28

• (-7,0)

• (6,0)

• (-6,0)

• (7,0)

Solve the system of Equation (x,y)
–x + 9y = –5
x –5y = 1  

• (-4,-1)

• (4,1)

• (-4,1)

• (1,4)