**Algebra – Key Terms**

In this section, we are going to look at a few different key terms that relate to algebra.

Algebraic expressions contain letters that stand for variable values or unknown values:

- Variable values are values that can change. An example of when a letter is a variable value is a graph, such as the graph
*y*= 2*x*. - Unknown values for terms are found by solving the equation that we are either given or equations that are created from information that we are given. An example would be:
*x*+ 5 = 7.

**Terms & Expression**

A term is a number or letter that is on its own. An expression is a set of terms that are combined.

For example, here is an expression:

This is an expression because there are many terms that are joined together. In the expression above, there are 3 different terms, which are 10*x*^{2}, -7*x* and 24.

**Equations**

An equation is where there are two expressions that are equal to one another. With the example for the unknown value that we used earlier (

*x*+ 5 = 7), the expressions “

*x*+ 5” and “7” are equal to one another.

**Identity**

An identity is a statement that is true no matter what values are chosen for the unknowns. The symbol for an identity is ≡. An example of an identity is:

The left and right side of the identity will be the same for any value of

*y*. Let’s show that this is the case by subbing in*y*as 2. When we sub in*y*as 2, we need to remember BIDMAS; Brackets, Indices, Division, Multiplication, Addition and Subtraction (or BODMAS; the O in BODMAS stands for other).Let’s check anther value for

*y*. I am now going to let*y*be 3.This identity will hold for any value of

*y*and we will be looking at how we can prove this in a later section.