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Published byJulianna Robbins Modified over 8 years ago

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**Another method for solving systems of equations is elimination**

Another method for solving systems of equations is elimination. Like substitution, the goal of elimination is to get one equation that has only one variable. To do this by elimination, you add the two equations in the system together.

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**Solving Systems of Equations by Elimination**

Step 1 Write the system so that like terms are aligned. Step 2 Eliminate one of the variables and solve for the other variable. Step 3 Substitute the value of the variable into one of the original equations and solve for the other variable. Write the answers from Steps 2 and 3 as an ordered pair, (x, y), and check. Step 4

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**Example 1: Elimination Using Addition**

3x – 4y = 10 Solve by elimination. x + 4y = –2 Write the system so that like terms are aligned. Add the equations to eliminate the y-terms. Simplify and solve for x.

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Example 1 Continued Write one of the original equations. Substitute 2 for x. Write the solution as an ordered pair.

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Check It Out! Example 2 y + 3x = –2 Solve by elimination. 2y – 3x = 14 Write the system so that like terms are aligned. Add the equations to eliminate the x-terms. Simplify and solve for y.

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**Check It Out! Example 2 Continued**

Write one of the original equations. Substitute 4 for y. Write the solution as an ordered pair.

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When two equations each contain the same term, you can subtract one equation from the other to solve the system. To subtract an equation add the opposite of each term.

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**Example 3: Elimination Using Subtraction**

2x + y = –5 Solve by elimination. 2x – 5y = 13 2x + y = –5 Add the opposite of each term in the second equation. –(2x – 5y = 13) 2x + y = –5 –2x + 5y = –13 Eliminate the x term. Simplify and solve for y.

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Example 3 Continued Write one of the original equations. Substitute –3 for y. Simplify and solve for x. Write the solution as an ordered pair.

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**Remember to check by substituting your answer into both original equations.**

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Check It Out! Example 4 3x + 3y = 15 Solve by elimination. –2x + 3y = –5 Add the opposite of each term in the second equation. Eliminate the y term. Simplify and solve for x.

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**Check It Out! Example 4 Continued**

Write one of the original equations. Substitute 4 for x. Simplify and solve for y.

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