Download Notes and Practice - Warren County Schools

1-6 Variables and Algebraic Expressions
Warm Up
Evaluate.
1. 5(7) – 1
34
2. 7(18 – 11)
49
3. 22 + 16 ÷ 8 + 3
4. 36 + 15(40 – 35)
5. 33 + 7(12 – 4)
27
111
83
1-6 Variables and Algebraic Expressions
Learning Target 3
I can evaluate an algebraic expression.
1-6 Variables and Algebraic Expressions
Vocabulary
variable
constant
coefficient
algebraic expression
evaluate
substitute
1-6 Variables and Algebraic Expressions
Harrison Ford was born in 1942. You can find
out what year Harrison turned 18 by adding
the year he was born to his age.
1942 + 18
In algebra, letters are often used to represent
numbers. You can use a letter such as a to
represent Harrison Ford’s age. When he turns a
years old, the year will be
1942 + a.
1-6 Variables and Algebraic Expressions
The letter a has a value that can change, or
vary. When a letter represents a number that
can vary, it is called a variable. The year 1954
is a constant because the number cannot
change.
An algebraic expression consists of one or
more variables. It usually contains constants
and operations. For example, 1942 + a is an
algebraic expression for the year Ron Howard
turns a certain age.
1-6 Variables and Algebraic Expressions
Age
Year born + age = year at age
16
18
21
1954 + 16
1954 + 18
1954 + 21
1970
1972
1975
36
1954 + 36
1990
a
1954 + a
To evaluate an algebraic expression,
substitute a number for the variable.
1-6 Variables and Algebraic Expressions
Additional Example 1: Evaluating Algebraic
Expressions
Evaluate k + 9 for each value of k.
A. k = 5
k+9
5+9
14
B. k = 2
Substitute 5 for k.
Add.
k+9
2+9
11
Substitute 2 for k.
Add.
1-6 Variables and Algebraic Expressions
Additional Example 2: Evaluating Algebraic
Expressions Involving Order of Operations
B. s ÷ 5 + s, for s = 15
15 ÷ 5 + 15
3 + 15
18
C. 5x2 + 3x, for x = 2
5(2)2 + 3(2)
5(4) + 3(2)
20 + 6
26
Substitute 15 for s.
Divide.
Add.
Substitute 2 for x.
Evaluate the power.
Multiply.
Add.
1-6 Variables and Algebraic Expressions
Check It Out: Example 2A
Evaluate the expression for the given value of
the variable.
A. 3x – 2 for x = 3
3(3) – 2
Substitute 3 for x.
9–2
Multiply.
7
Subtract.
1-6 Variables and Algebraic Expressions
Check It Out: Example 2
B. r ÷ 3 + r, for r = 12
12 ÷ 3 + 12
4 + 12
16
C. 4y2 + 2y, for y = 3
4(3)2 + 2(3)
4(9) + 2(3)
36 + 6
42
Substitute 12 for r.
Divide.
Add.
Substitute 3 for y.
Evaluate the power.
Multiply.
Add.
1-6 Variables and Algebraic Expressions
Additional Example 3: Evaluating Algebraic
Expressions with Two Variables
Evaluate 6
a + 4b, for a = 3 and b = 2.
6
a + 4b
6
+ 4(2)
3
2+8
10
Substitute 3 for a and 2 for b.
Divide and multiply from
left to right.
Add.
1-6 Variables and Algebraic Expressions
Check It Out: Example 3
8
Evaluate w
+ 2x, for w = 4 and x = 2.
8
w + 2x
8
+ 2(2)
4
Substitute 4 for w and 2 for x.
2+4
Divide and multiply from
left to right.
6
Add.
1-6 Variables and Algebraic Expressions
Lesson Quiz—Have you mastered the target?
Put your name on a half sheet of paper. Work the
problem and write the letter choice that matches
your answer.
1. Evaluate m + 4 for m = 19.
A. 21
B. 27
C. 23
D. 28
1-6 Variables and Algebraic Expressions
Lesson Quiz for Student Response Systems
2. Evaluate 7x – 8 for x = 5.
A. 20
B. 27
C. 22
D. 32
1-6 Variables and Algebraic Expressions
Lesson Quiz for Student Response Systems
3. Evaluate 6x2 + 5x for x = 5.
A. 185
B. 85
C. 175
D. 50
1-6 Variables and Algebraic Expressions
Lesson Quiz for Student Response Systems
4. Evaluate 39 + 5y for x = 3 and y = 5.
y
A. 38
B. 44
C. 54
D. 64
1-6 Variables and Algebraic Expressions
Lesson Quiz for Student Response Systems
5. The expression 12n gives the number of
months in n years. Evaluate 12n for n = 3.
How many months are in 3 years?
A. 12 months
B. 24 months
C. 36 months
D. 48 months
1-6 Variables and Algebraic Expressions
Homework
• Do the circled problems on the back of
your notes page.
• Show your substitutions!!!
• Show the order of operations when
necessary.