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Expressions and variables

An algebraic expression comprises both numbers and variables together with at least one arithmetic operation.


\\ 4\cdot x-3 \\

A variable, as we learned in pre-algebra, is a letter that represents unspecified numbers. One may use a variable in the same manner as all other numerals:


To evaluate an algebraic expression you have to substitute each variable with a number and perform the operations included.


Evaluate the expression when x=5

\\ 4\cdot x-3 \\

First we substitute x with 5

\\ 4\cdot 5-3 \\

And then we calculate the answer

\\ 20-3=17 \\

An expression that represents repeated multiplication of the same factor is called a power e.g.

\\ 5\cdot 5\cdot 5=125 \\

A power can also be written as

\\ 5^3=125 \\

Where 5 is called the base and 3 is called the exponent. The exponent corresponds to the number of times the base is used as a factor.

\\ 5^3=5\cdot 5\cdot 5 \\


Videolesson: Evaluate the expression when x=4 and y=3

\\5x + y^{2}- xy \\

Next Class:  Discovering expressions, equations and functions, Operations in the right order