1. Expressions

2. The Vocabulary of Expressions
Algebraic Expression = consists of variables, numbers and operations.
Examples: 5, x, 5x, 5x + 2, 5x(x – 5)
Variable = an unknown or changing number, often represented by “x”. Example: In the expression 2x – 3 , x is the variable because it changes.
Constant = a number that doesn’t change
Example: In the expression 2x – 3 , 3 is the constant because 3 is
always 3 – it is constant.
Coefficient = the number that is multiplied to a variable
  Example: In the expression 2x – 3 , 2 is the coefficient because it is multiplied
to the variable x.
Terms = values separated by operations (plus and minus signs). 
Example: In the expression 2x – 3 there are two terms, the 2x and the 3.
In the expression 5m + 2x – 3 there are three terms, the 5m, 2x and
the 3.

3. This is what we are talking about…

4. Math is a foreign language…
Common Words and Phrases for:
Add
Subtract
Multiply
Divide
Equals
plus
add
sum
more than
in addition to
greater than
total
and
difference
subtract
less than
take away
product of
times
twice (×2)
factor
divided by
quotient
split
share
distribute is

5. Translating from English to Math…
The students in Math 7 have 2 pets each.
x = the number of students
(any letter or symbol will do, even a smiley face!) 2x
is the algebraic expression or math translation

6. One more example…
Salena makes $25 an hour and spends $15 a day on gas. Write an algebraic expression that shows Salena’s earnings in one day. The variable is the number of hours (we don’t know what this is and it may not be the same everyday) so let’s use h for hours. 25h – 15

7. Simplifying Expressions…
Adding and subtracting like terms.
***You can only add and subtract terms that
have the same variable!!!
***You add and subtract the coefficients.
(This means that you can not add x to y and get 2xy.)
Such as…
3x + 6 x = 9x
5m – 2m + 1 = 3m + 1
k – 4 – 4k = -3k – 4
(remember, k is the same as 1k and
–k is the same as -1k)

8. Click on this link to practice simplifying a few expressions