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Solve a System of Linear Equations by Graphing

In the following exercises, solve the following systems of equations by graphing.

{ 3 x + y = 6 x + 3 y = −6

( 3 , −3 )
This figure shows a graph on an x y-coordinate plane of 3x plus y = 6 and x plus 3y = negative 6.

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{ y = x 2 y = −2 x 2

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{ 2 x y = 6 y = 4

( 5 , 4 )
This figure shows a graph on an x y-coordinate plane of 2x – y = 6 and y = 4.

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{ 2 x y = 5 4 x 2 y = 10

coincident lines
This figure shows a graph on an x y-coordinate plane of 2x – y = 5 and 4x – 2y = 10.

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{ x + 2 y = 4 y = 1 2 x 3

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Determine the Number of Solutions of a Linear System

In the following exercises, without graphing determine the number of solutions and then classify the system of equations.

{ y = 2 5 x + 2 −2 x + 5 y = 10

infinitely many solutions, consistent system, dependent equations

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{ 3 x + 2 y = 6 y = −3 x + 4

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{ 5 x 4 y = 0 y = 5 4 x 5

no solutions, inconsistent system, independent equations

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{ y = 3 4 x + 1 6 x + 8 y = 8

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Solve Applications of Systems of Equations by Graphing

LaVelle is making a pitcher of caffe mocha. For each ounce of chocolate syrup, she uses five ounces of coffee. How many ounces of chocolate syrup and how many ounces of coffee does she need to make 48 ounces of caffe mocha?

LaVelle needs 8 ounces of chocolate syrup and 40 ounces of coffee.

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Eli is making a party mix that contains pretzels and chex. For each cup of pretzels, he uses three cups of chex. How many cups of pretzels and how many cups of chex does he need to make 12 cups of party mix?

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Section 5.2 Solve Systems of Equations by Substitution

Solve a System of Equations by Substitution

In the following exercises, solve the systems of equations by substitution.

{ 3 x y = −5 y = 2 x + 4

( −1 , 2 )

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{ 3 x 2 y = 2 y = 1 2 x + 3

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{ x y = 0 2 x + 5 y = −14

( −2 , −2 )

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{ y = −2 x + 7 y = 2 3 x 1

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{ y = −5 x 5 x + y = 6

no solution

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{ y = 1 3 x + 2 x + 3 y = 6

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Solve Applications of Systems of Equations by Substitution

In the following exercises, translate to a system of equations and solve.

The sum of two number is 55. One number is 11 less than the other. Find the numbers.

The numbers are 22 and 33.

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The perimeter of a rectangle is 128. The length is 16 more than the width. Find the length and width.

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The measure of one of the small angles of a right triangle is 2 less than 3 times the measure of the other small angle. Find the measure of both angles.

The measures are 23 degrees and 67 degrees.

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Gabriela works for an insurance company that pays her a salary of $32,000 plus a commission of $100 for each policy she sells. She is considering changing jobs to a company that would pay a salary of $40,000 plus a commission of $80 for each policy sold. How many policies would Gabriela need to sell to make the total pay the same?

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Section 5.3 Solve Systems of Equations by Elimination

Solve a System of Equations by Elimination In the following exercises, solve the systems of equations by elimination.

{ x + y = 12 x y = −10

( 1 , 11 )

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{ 4 x + 2 y = 2 −4 x 3 y = −9

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{ 3 x 8 y = 20 x + 3 y = 1

( 4 , −1 )

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{ 3 x 2 y = 6 4 x + 3 y = 8

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{ 9 x + 4 y = 2 5 x + 3 y = 5

( −2 , 5 )

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{ x + 3 y = 8 2 x 6 y = −20

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Solve Applications of Systems of Equations by Elimination

In the following exercises, translate to a system of equations and solve.

The sum of two numbers is −90 . Their difference is 16 . Find the numbers.

The numbers are −37 and −53 .

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Omar stops at a donut shop every day on his way to work. Last week he had 8 donuts and 5 cappuccinos, which gave him a total of 3,000 calories. This week he had 6 donuts and 3 cappuccinos, which was a total of 2,160 calories. How many calories are in one donut? How many calories are in one cappuccino?

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Practice Key Terms 1

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Source:  OpenStax, Elementary algebra. OpenStax CNX. Jan 18, 2017 Download for free at http://cnx.org/content/col12116/1.2
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