Transcript Objectives Use variables to represent unknown quantities

1.2 Variables, Expressions, and Equations
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Objectives
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Use variables to represent
unknown quantities.
Represent real-world situations
with equations and solve by
guess-and-check.
Glossary Terms
Variable – letters used to represent
unknown quantities
algebraic expression
- combining
numbers and variables using addition,
subtraction, multiplication and
division
Equation – two expressions connected
by an equal sign
solution to an equation – all values of
the variable that make the equation
true
At City Park you can rent in-line skates and protective gear for
$2 per hour plus a $4 fee. Write an expression that
represents the cost of renting skates and then write an
equation that relates the expression to a total cost of $10.
Number of Hours
1
Expression for cost
4 + 2(1)
2
4 + 2(2)
3
4 + 2(3)
The rental cost is 4 + 2 times the # of hours
4 + 2h
If the total cost of renting the skates is $10,
the equation relating the expression to
the cost is : 4 + 2h = 10
When one side of an equation has the same value as the other
side, the equation is said to be true.
To determine whether an equation is true or not
simplify both sides of the equation.
4 + 2(3) = 6 + 2(2)
4+6=6+4
10 = 10
The left and right sides of
the equation have the same
value, therefore the equation
is true.
Remember, the solution to an equation
is the value(s) of the variable that makes
the equation true.
Jessica places 3 photos on the cover of her photo album. She
places 4 photos on each of the other pages. She has 155
photos in all. How many pages will she need if she uses
all her photos?
Let p equal the number of pages in the photo
album. So the equation will be 4p + 3 = 155
Use guess and check to solve
Try p = 20
4(20) + 3 = 155
80 + 3 = 155
83 = 155
Too low.
Try p = 40
4(40) + 3 = 155
160 + 3 = 155
163 = 155
Too high.
Try p = 38
4(38) + 3 = 155
152 + 3 = 155
155 = 155
So she needs 38 pages
1.2 Variables, Expressions, and Equations
Key Skills
Evaluate expressions for given
values of the variable.
Evaluate 5x – 7 for x = 2 and x = 6.
Evaluate for x = 2 Evaluate for x = 6
5(2) – 7
5(6) – 7
10 – 7
3
30 – 7
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Key Skills
Write an equation to represent a
problem situation.
Membership in a gym at a community
center costs $15 per month plus a
one-time fee of $50.
Write an equation for the total cost, c,
for membership over m months.
The cost is $50 plus $15 every month.
c = 50 + 15m
TOC
Assignment
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Page 16 – 17
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# 10 – 30 even, 31 – 39, 44 – 48
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When you get to 44 – 48 you will
have to THINK!!!!