Download Evaluating and Writing Algebraic Expressions

EVALUATING AND
WRITING ALGEBRAIC
EXPRESSIONS
Mrs. Rauch
Day 1
Learning Target:
I can evaluate algebraic expressions for
specific values of variables.
Team member #2 please get:
•
A marker for each person in your group
•
One rag per table
What is an Algebraic Expression?
•
An expression consists of a combination of numbers, operation symbols, and grouping
symbols such as parentheses ( ). An algebraic expression is an expression that contains
one or more variables, but NO equals sign!
•
Expressions:
Algebraic Expressions
3+4
6–2
3 (c + 8)
2a
(6 + 3) -1
9–x
What is a variable?
A variable…
•
Is a letter or symbol that represents an unknown number.
•
Can be any letter.
•
When the same letter is used more than once it represents the same value
The parts of an expression separated by the
operation symbols are known as terms.
•
Terms may have a variable.
•
Variables may have a coefficient. A coefficient is a number getting multiplied by a
variable.
•
Terms without a variable are known as constants.
Let’s Try! Given the expression below:
•
How many terms are in the expression?
•
Underline each coefficient.
•
Circle each constant.
•
Put a box around each variable
5x + 3 – 2x
Now we are ready to evaluate Algebraic
Expressions.
How do you think this is done?
For example, if you are given the expression r + 5 and I tell you that r = 5, what steps
would you take?
1.) Rewrite the expression replacing the variable with its value
2.) Follow order of operations to simplify and evaluate the expression
3.) Circle final outcome.
Remember!
In expressions, there are many different ways
to write multiplication
1)
2)
3)
4)
5)
ab
a•b
a(b) or (a)b
(a)(b)
axb
We are not going to use the multiplication symbol any more.
Why?
Division, on the other hand, is written as:
𝑥
1)
3
2) x ÷ 3
Let’s Practice!
Evaluate each expression when a = 12
1) a + 3
2)
17 – a
Evaluate the following when n = 4
1)
9n
(what operation does this mean when a number is right beside a variable?
Look at your notes if you don’t know)
2) 40 / n
Now, let’s try two operations!
1.)
7x + 4 for x = 6
2.)
8y – 22 for y = 9
3.)
12
𝑥
4.)
y + 3z for y = 5 and z = 6
+8
for 4
Time to apply what we’ve learned!
•
Team member # 4 please return markers, and rags.
Day 2
Learning Target:
I can translate written phrases into algebraic expressions.
When solving real-world problems, you will need to translate
words, or verbal expressions, into algebraic expressions
.
For example, Katie and Aaron both donated canned
foods for the Holiday food drive, but Aaron donated five
times the amount Katie did. The amount Aaron donated
can be found using the expression 5x .
What would x represent?
What word(s) tell you to multiply?
In order to translate a phrase into an algebraic expression, we
must first review some synonyms for the basic operations.
Remember!
•
Multiplication expressions should be written in side-by-side form, with the
number always in front of the variable.
3a
•
2t
1.5c
0.4f
Division expressions should be written using the fraction bar instead of the
traditional division sign.
Addition phrases:
• 3 more than a number t
•
the sum of 10 and a number
•
a number increased by 4.5
Subtraction phrases:
• a number y decreased by 4
•
the difference between 10 and a number
•
6 less than a number
Multiplication phrases:
• the product of 3 and a number
•
twice the number n
•
4.2 times a number p
Division phrases:
•
the quotient of 25 and a number
•
the number y divided by 2
•
2.5 divide g
Let’s try it!
•
Write an algebraic expression for
1) m increased by 5
2) 8 less than a number x
3)
a number r divided by 15
4) 2 7 times the sum of x and t
5)
11 less than 4 times a number y
6)
two more than 6 times a number
Write a verbal expression for:
1)
8 + a.
2) 3(x)
3) 2x + 9