Chapter 4 Systems of Equations

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Chapter 4Systems of Equations

• 4.1 Systems of Equations in Two Variables

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A system of two linear equations in two variables
x and y consists of two equations, Ax By C
and Dx Ey F
A solution of a system of linear equations in two
variables is an ordered pair (x, y) that
satisfies both equations.
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Lines intersect one solution
Lines are parallel no solution
Lines coincide infinitely many solutions
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Check, by graphing, whether each system of 3
equations has a common solution. If it does, give
the solution. If it does not, state that it does
not.
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Check, by graphing, whether each system of 3
equations has a common solution. If it does, give
the solution. If it does not, state that it does
not.
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Without graphing, tell whether or not the
following system, in which a ? b, has a solution,
and if so what it is. If it does not have a
solution, explain why not.
Explain why your answer above does not depend on
the values of a and b, as long as a ? b.
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A Put each of the equations in the following
system into slope intercept form.
B From your answer to A, and without graphing,
tell whether the graphs of the two equations
intersect once, do not intersect, or define the
same line.
C Based on your answer to part B, describe a
general method for determining the nature of the
solution(s) of a linear system without graphing.
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HW 4.1Pg 161 1-15 Odd, 16-18
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HW Quiz 4.1Friday, April 19, 2013
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4.2 Solving Systems of Equations
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Objective Solve systems of linear equations by
substitution
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Objective Solve systems of linear equations by
substitution
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A
B
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Objective Solve systems of linear equations by
Linear Combinations
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Objective Solve systems of linear equations by
Linear Combinations
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D
C
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4.3 Using Systems of Equations
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You and a friend share the driving on a 280 mile
trip. Your average speed is 58 miles per hour.
You friends average speed is 53 miles per hour.
You drive one hour longer than your friend. How
many hours did each of you drive?
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A gardener has two solutions of weedkiller and
water. One is 5 weedkiller and the other is 15
weedkiller. The gardener needs 100 L of a
solution that is 12 weedkiller. How much of each
solution should she use?
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A freight train leaves Tyler, traveling east at
35 km/h. One hour later a passenger train leaves
Tyler, also traveling east on a parallel track at
40 km/h. How far from Tyler will the passenger
train catch the freight train?
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E The band boosters are organizing a trip to a
national competition for the 226-member marching
band. A bus will hold 70 students and their
instruments. A van will hold 8 students and their
instruments. A bus costs 280 to rent for the
trip. A van costs 70 to rent for the trip. The
boosters have 980 to use for transportation.
Write a system of equations whose solution is how
many buses and vans should be rented. Solve the
system.
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HW 4.2-3Pg 166-167 1-25 odd, 26-29Pg 173 27-33
Odd, 34
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HW Quiz 4.2-3Friday, April 19, 2013
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4.4 Systems of Equations in Three Variables
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An Equation with Three Variables

• A solution of a system of equations in three
  variables is called an ordered triple.
• What is an ordered triple?
• ( x, y, z) An example is (2 , -4, 3).
• This ordered triple must be true for all the
  equations in the system.

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• The graph of a linear equation in three variables
  is a plane. Thus, if a system of equations in
  three variables has a unique solution, it is a
  point common to all of the planes.

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How should we solve a system in three variables??

• We will first solve this equation
• x y z 4
• x - 2y - z 1
• 2x- y -2z -1

These numbers indicate the equations in the
first, second, and third positions.
First, pick a variable to eliminate. We will
eliminate x in this system.
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Solving a system of three equations

• x y z 4
• x - 2y - z 1
• 2x- y -2z -1

Step 3 -3y -2z -3 -3y -4z -9
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Solving a system of three equations continued

• Next part of Step 3

Now just substitute in 3 for z and find the other
variables.
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The Answers

• You should have gotten

x 2
y -1
z 3
The ordered triple is (2, -1, 3)
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Lets do ANOTHER example!

• Lets solve this system of equations
• 2x y 2z 11
• 3x 2y 2z 8
• x 4y 3z 0

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Solving the system of equations continued
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Solving the system of equations continued

• Now plug in 6 for the variable z to find x and y.
  
• You should get

x 2
y -5
z 6
The ordered triple is (2, -5, 6)
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And yet ANOTHER example!

• But this one has a special twist!
• Systems of three equations can have infinite many
  solutions or no solutions.
• Here is an example with infinite many solutions

x 3y z 1 2x y 2z 2 x 2y
3z -1
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Solving a system of equations that has infinite
many solutions continued
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Summary

• Remember, solutions are written as an ordered
  triple.
• Remember, solutions can also be no solution or
  infinite many solutions.
• If one equation is missing a variable, just line
  it up with the other equations.
• For example 3p 2r 11
• q - 7r 4
• p - 6q 1
• Check your solutions in all equations to make
  sure it is correct. Just because it answers two
  of them, doesnt mean it answers all of them.

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B
A
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HW 4.4 Pg 178-179 1-27 Odd, 28-30
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4.4 Systems of Equations in Three Variables
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Groups to work on solving
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HW 4.4b Pg 178-179 2-26 Even
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HW Quiz 4.4bFriday, April 19, 2013
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4.5 Using a System of Three Equations
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In yesterdays swim meet, Roosevelt High
dominated in the individual events, with 24
individual-event placers scoring a total of 56
points. A first-place finish scores 5 points, a
second-place finish scores 3 points, and a
third-place finish scores 1 point. Having as many
third-place finishers as first- and second-place
finishers combined really shows the teams depth.
Use a system of three equations in 3 variables
to determine the number of 1st, 2nd, and 3rd
place finishers Roosevelt had.
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You have 25 to spend on picking 21 pounds of
three different types of apples in an orchard.
The Empire apples cost 1.40 per pound, the Red
Delicious apples cost 1.10 per pound, and the
Golden Delicious apples cost 1.30 per pound. You
want twice as many Red Delicious apples as the
other two kinds combined. Write a system of
equations to represent the given information.
How many pounds of each type of apple should you
buy?
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Gina sells magazines part time. On Thursday,
Friday, and Saturday, she sold 66 worth. On
Thursday she sold 3 more than on Friday. On
Saturday she sold 6 more than on Thursday. How
much did she take in each day?
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Find a three digit positive integer such that the
sum of all three digits is 14, the tens digit is
two more than the ones digit, and if the digits
are reversed the number is unchanged.
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HW 4.5Pg 181-182 1-17 Odd, 18-19
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4.6 Consistent and Dependent Systems
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Objective Determine whether a system of
equations is consistent or inconsistent.
Consistent System If a system of equations has
at least one solution
Inconsistent System If a system of equations
has no solution
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Objective Determine whether a system of
equations is consistent or inconsistent.
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Objective Determine whether a system of
equations is dependent
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• Is it possible to have a system that is
  consistent and dependent?
• Is it possible to have a system that is
  inconsistent and dependent?
• Is it possible to have an inconsistent system
  that is not dependent?
• Is it possible to have an consistent system that
  is not dependent?

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Objective Determine whether a system of
equations is dependent
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Determine if the systems are consistent,
inconsistent and dependent
B
A
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HW Quiz 4.5Friday, April 19, 2013
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HW 4.6Pg 186-187 1-23 Odd, 25-31
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HW Quiz 4.6Friday, April 19, 2013
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4.7 Systems of Linear Inequalities
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Objective Graph a linear inequality
The boundary line of the inequality divides the
coordinate plane into two half-planes a shaded
region containing the points that are solutions
of the inequality, and an unshaded region which
contains the points that are not.
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Objective Graph a linear inequality
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Objective Graph a system of linear inequalities
A system of linear inequalities is two or more
linear inequalities in the same variables and is
also called a system of inequalities.
A solution of a system of linear inequalities is
an ordered pair that is a solution of each
inequality in the system.
The graph of a system of linear inequalities is
the graph of all solutions of the system.
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Objective Graph a system of linear inequalities
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Objective Graph a system of linear inequalities
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Objective Graph a system of linear inequalities
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Objective Graph a system of linear inequalities
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HW 4.7Pg 192 1-39 Odd, 40-41
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4.8 Using Linear Programming
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Objective Solve problems using linear
programming.
A bakery is making whole-wheat bread and apple
bran muffins. For each batch of bread they make
35 profit. For each batch of muffins they make
10 profit. The bread takes 4 hours to prepare
and 1 hour to bake. The muffins take 0.5 hour to
prepare and 0.5 hour to bake. The maximum
preparation time available is 16 hours. The
maximum baking time available is 10 hours. How
many batches of bread and muffins should be made
to maximize profits?
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Objective Solve problems using linear
programming.
Optimization means finding the maximum or minimum
value of some quantity.
Linear programming is the process of optimizing a
linear objective function subject to a system of
linear inequalities called constraints.
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Objective Solve problems using linear
programming.
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Objective Solve problems using linear
programming.
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Objective Solve problems using linear
programming.
A bakery is making whole-wheat bread and apple
bran muffins. For each batch of bread they make
35 profit. For each batch of muffins they make
10 profit. The bread takes 4 hours to prepare
and 1 hour to bake. The muffins take 0.5 hour to
prepare and 0.5 hour to bake. The maximum
preparation time available is 16 hours. The
maximum baking time available is 10 hours. How
many batches of bread and muffins should be made
to maximize profits?
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Objective Solve problems using linear
programming.
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Objective Solve problems using linear
programming.
Wheels Inc. makes mopeds and bicycles. Experience
shows they must produce at least 10 mopeds. The
factory can produce at most 60 mopeds and 120
bicycles per month. The profit on a moped is 134
and on a bicycle, 20. They can make at most 160
units combined. How many of each should they make
per month to maximize profit?
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Objective Solve problems using linear
programming.
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Objective Solve problems using linear
programming.
You are planning to have roast pork and twice
baked potatoes for dinner. You want to consume at
least 250 grams of carbohydrates, but no more
than 60 grams of fat per day. So far today you
have consumed 170 grams of carbohydrates and 30
grams of fat. The table below shows the number of
grams of carbohydrates, fat, and protein in a
serving of roast pork and twice baked potatoes.
How many servings of each can you eat to fulfill
your daily requirements for carbohydrates and fat
while maximizing the amount of protein you
consume?
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Objective Solve problems using linear
programming.
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HW 4.8 Pg 195 1-6
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HW Quiz 4.8Friday, April 19, 2013
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Test Review

• Part 1

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Find a and b so that the system below has the
unique solution (-2, 3)
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Find p and q so that the graph of the equation y
x2 px q passes through (-1, 3) and (2, 4)
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Know the terms Dependent, Consistent, and
Inconsistent
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Part 2

• Part two will consist of three linear programming
  problems along with one proof

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HW R-4Pg 200 1-13 Study All Challenge Problems
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