To solve a system by substitution, you solve one equation for one variable and then substitute this expression into the other equation.

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To solve a system by substitution, you solve one
equation for one variable and then substitute
this expression into the other equation.
Use substitution to solve the system of equations.
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Use substitution to solve the system of equations.
3
Use substitution to solve the system of equations.
4
For the elimination method, you get rid of one of
the variables by adding or subtracting equations.
You may have to multiply one or both equations by
a number to create variable terms that can be
eliminated.
Use elimination to solve the system of equations.
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Use elimination to solve the system of equations.
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Find the solution to the system.
3x y 1
2y 6x 18
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Classify the system and determine the number of
solutions.
56x 8y 32
7x y 4
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Example 4 Zoology Application
A veterinarian needs 60 pounds of dog food that
is 15 protein. He will combine a beef mix that
is 18 protein with a bacon mix that is 9
protein. How many pounds of each does he need to
make the 15 protein mixture?
Let x present the amount of beef mix in the
mixture.
Let y present the amount of bacon mix in the
mixture.
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Example 4 Continued
Write one equation based on the amount of dog
food
Write another equation based on the amount of
protein
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Check It Out! Example 4
A coffee blend contains Sumatra beans which cost
5/lb, and Kona beans, which cost 13/lb. If the
blend costs 10/lb, how much of each type of
coffee is in 50 lb of the blend?
Let x represent the amount of the Sumatra beans
in the blend.
Let y represent the amount of the Kona beans in
the blend.
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Check It Out! Example 4 Continued
Write one equation based on the amount of each
bean
Write another equation based on cost of the beans
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Homework pg. 194s 22, 33, 36, 37