Download 3.1 Systems of Linear Equations (Elimination – or as the book calls it

3.1 Systems of Linear
Equations (Elimination – or as
the book calls it, Addition
Method)
Elimination Method (Addition
Method):
1.
1.
2.
3.
4.
5.
If necessary, rewrite both equations in the form
Ax + By = C.
If necessary, multiply either equation or both equations
by appropriate nonzero numbers so that the sum of the xcoefficients or the sum of the y-coefficients is 0.
Add the equations in step 2. The sum will be an
equation in one variable.
Solve the equation in one variable.
Back-substitute the value obtained in step 4 into either of
the given equations and solve for the other variable.
Check the solution in both of the original equations.
Example 1:
Solve by the addition method: (elimination)
4x – 7y = -16
2x + 5y = 9
Example 2:
Solve by the addition method: (elimination)
3x = 2 – 4y
5y = -1 – 2x
Example 3:
Solve by the addition method: (elimination)
3x – 2y = 5
2
2
x – 5y = - 3
2
2
Example 4:
Solve the system:
5x – 2y = 4
-10x + 4y = 7
Example 5:
Solve the system:
x = 4y – 8
5x – 20y = -40
Homework:
Pages 177-178
43 – 81 odds
20 total