Digits, Grade 8, Volume 2, Homework Helper

15-6: Solving Simultaneous Linear Equations Using Addition

You can solve linear systems using an algebraic method called the addition method.

In the addition method, you solve the system by adding the equations to eliminate one of the variables.

Solve the system by addition.

table with 2 rows and 1 column , row1 column 1 , x plus y equals minus 1 , row2 column 1 , 3 x minus y equals 5 , end table

Step 1 Solve for the first variable.

Addition method.

Step 2 Solve for the second variable.

table with 3 rows and 3 columns , row1 column 1 , cap write , , either , , equation , . , column 2 x plus y , column 3 equals minus 1 , row2 column 1 , cap substitute . 1 for bold x . , column 2 1 plus y , column 3 equals minus 1 , row3 column 1 , cap solve , for bold y . , column 2 y , column 3 equals minus 2 , end table

Step 3 Write the solution.

Since x = 1 and y = −2, the solution is (1, −2).

Step 4 Check your solution.

Substitute the solution (1, −2) into each equation.

Checking the solution.


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Table of Contents

Digits, Grade 8, Volume 2, Homework Helper Unit D: Two-Dimensional Shapes Unit E: Measurement and Data Unit F: Personal Financial Literacy Unit G: Step-Up Lessons English/Spanish Glossary Formulas Math Symbols Formulas Measures Properties