1. Solving Systems of Equations
Substitution Method
Liberty Hill Middle School
Mrs. Book
Algebra I
11/14/2018

2. Substitution Method
You can create a one-variable equation by replacing one variable with an equivalent expression containing the other variable.
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3. Steps for Using the Substitution Method
Step 1: Solve one of the equations for one of the variables
Step 2: Substitute the expression from Step 1 into the other equation and solve for the other variable
Step 3: Substitution the value from Step 2 into one of the original equations and solve.
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4. Solve the system of linear equations by substitution
y = -2x – 9
6x – 5y = -19
Equation 1 is already solved for y
Substitute -2x – 9 for y in Equations 2 and solve for x
6x – 5(-2x – 9) = - 19
6x + 10x + 45 = -19
16x = -45 – 19
16x = -64
x = -4
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5. Solve the system of linear equations by substitution
y = -2x – 9
6x – 5y = -19
x = -4
Substitute -4 in for x in Equation 1 and solve for y
y = -2(-4) – 9
y = 8 – 9
y = -1
The solution is (-4, -1)
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6. *
07/16/96
Solve the system of linear equations by substitution. Check your solution.
y = 3x + 14
y = -4x
(-2, 8)
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7. *
07/16/96
Solve the system of linear equations by substitution. Check your solution.
3x + 2y = 0
y = ½x - 1
(½, -¾)
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8. *
07/16/96
Solve the system of linear equations by substitution. Check your solution.
-x + y = 3
3x + y = - 1
(-1, 2)
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9. *
07/16/96
Solve the system of linear equations by substitution. Check your solution.
x - 2y = 7
3x - 2y = 3
(-2, -9/2)
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10. Summary Solve one equation for one of the variables
Substitution the expression from Step 1 into the other equation and solve for the other variable
Substitute the value from Step 2 into one of the original equation and solve.
11/14/2018