1. Goal: To solve a system of equations by elimination
Warm-up: For each system of equations, add the top equation to the
bottom equation:
3x + 5y = 20 2. 3x - 2y = 6 3. -x + y = 71.
-2x - 5y = -15 2x + 2y = 4 x - 3y = -5
What do you notice happens for all 3 of these problems?
This gives us another method to solve a system of equations called
elimination. The goal of solving by elimination, just like solving by
substitution, is to take 2 equations with two variables and reduce it to
one equation with one variable by adding together the equations such
that one of the variable's coefficients add to zero (eliminating the
variable), making it easier to solve.
Multiply, if necessary, one or both equations by a constant so at
least one pair of like terms has opposite coefficients.
1.
Add the equations to eliminate one of the variables2.
Solve the resulting equation.3.
Substitute the value from step 3 into one of the original equations
and solve for the other variable.
4.
Check your solution.5.
Steps:
Examples: Solve the following systems, and check your solution.
3/9: Introduction to Elimination
Thursday, March 5, 2015 9:33 PM
ch 5 Systems Page 1

2. Examples: Solve the following systems, and check your solution.
3x + 5y = 201.
-2x - 5y = -15
2. 3x - 2y = 6
2x + 2y = 4
3. -x + y = 7
ch 5 Systems Page 2

3. 3. -x + y = 7
x - 3y = -5
Assignment: Page 251: 4, 6
ch 5 Systems Page 3