Solving System of Equations by Substiution

1.Solve one equation for __ or __.

2.________ this expression into the other equation and _____ for the variable.

3. _____ your answer into the revised equation from Step 1 and _______ for the other variable.

​Steps to Solving

A method of solving systems of equations by substituting equations within one another.

Substitution Method

When is it best to use substitution over graphing?

Examples

Which problem would be better for solving by graphing and which would be better by substitution?

2. y = 6x

2x + 3y = -20

1. y = 4x -1

   y = 2x - 5 

3. x + 5y = 4

   3x + 5y = -1

Fill in the Blank

Solve the following system by substitution. Write your answer as an ordered pair. (x,y). No spaces.

$$y=x+9;\ 3x+8y=-5$$

Fill in the Blank

Solve the following system by substitution. Write your answer as an ordered pair. (x,y). No spaces.

$$x=4y+7;\ 2x-6=12$$

Fill in the Blank

Solve the following system by substitution. Write your answer as an ordered pair. (x,y). No spaces.

$$2x+y=-2;\ 5x+3y=-8$$

Fill in the Blank

Solve the following system by substitution. Write your answer as an ordered pair. (x,y). No spaces.

$$2x-3y=-11;\ 2x+y=9$$

Fill in the Blank

Solve the following system by substitution. Write your answer as an ordered pair. (x,y). No spaces.

$$x+4y=0;\ \ 3x+2y=20$$

Fill in the Blank

Solve the following system by substitution. Write your answer as an ordered pair. (x,y). No spaces.

$$6x+3y=54;\ \ 2x+y=18$$

Fill in the Blank

Solve the following system by substitution. Write your answer as an ordered pair. (x,y). No spaces.

$$x-3y=-2;\ \ 10x+8y=-20$$

Fill in the Blank

Solve the following system by substitution. Write your answer as an ordered pair. (x,y). No spaces.

$$3x-y=-8;\ \ \ 5x+2y=5$$