writing and evaluating algebraic expressions


An expression is NOT an equation because it DOES NOT have an

equal sign.There are 2 types of expressions.

5 + 84 Numerical3x + 10

AlgebraicNotice there are no equal signs in

these expressions so they are not equations!


A numerical expression contains only

numbers and symbols and NO LETTERS. 5 times 3 plus 8

(5•3) + 8


An algebraic expression contains

only numbers, symbols, and variables. It is sometimes referred to as a variable expression. The product of 3 and x 3xThe sum of m and 8 m + 8The difference of r and 2 r - 2


What is a variable?A variable represents an unknown value.

1) 4 + x 2) 10 – ?

3) 5y 4) 20

A variable can be any letter of the alphabet since it represents an unknown.


Word Phrases for multiplication are:

The product of 5 and a number c

Seven times a number t

6 multiplied by a number d

5 • c or 5c

7 • t or 7t

6 • d or 6d


The Placement rule for multiplication is:

The product of 5 and a number c

Seven times a number t

6 multiplied by a number d

5 • c or 5c

7 • t or 7t

6 • d or 6d

Always write the variable AFTER the number.


Evaluate means to find the value of analgebraic expression by substitutingnumbers in for variables.

m = 26 + m ?6 + 2

8


Evaluate means to find the value of analgebraic expression by substitutingnumbers in for variables.

r = 37 + r ?7 + 3 10


Evaluate the variable expression when n = 6.

1) n 8 2) n 26 8

146 2

4

Evaluate just means solve by substitution.


Evaluate the variable expression when n = 6.

Evaluate just means solve by substitution.

3) 3n 4) n63 6

18661


Evaluate the algebraic expression when n = 8.

1) 56n

2) 20 n

568

7

20 8

12


Evaluate the expression if a = 3 and b = 4.

1) 3a b 2) 2b a3 43

9 413

2 34 8 3

5


Evaluate the expression if a = 3 and b = 4.

3) 2ab 4) 5 ab2 43

6 45 43 5 12

1724


Evaluate the expression if x = 5 and y = 3.

1) 3xy

33

5

1535

2) 2 2x y2 25 3

25 9

34


Take Out Your Study Guide!!!


An expression is NOT an equation because it does not have an equal sign. There are 2 types of expressions. NUMERICAL EXPRESSION: Contains only numbers and symbols. Example: 5 • 3 + 4

ALGEBRAIC EXPRESSION: Contains numbers, symbols, and variables. Also known as a variable expression. Example: m + 8

A VARIABLE is a letter or symbol that represents a number. Example: x

TYPES OF EXPRESSIONS #1


#2

Show the substitution. Show your work down. Circle your answer.

Show your work one step at a time down. No equal signs!

Evaluate means solve.

Evaluate if x = 3 and y = 4 22 x y

22(3 4)22(7)

2(49)98

writing and evaluating algebraic expressions

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