A variable is just a letter or symbol used to represent a number, or value that can change. For example one might write a short program that displays the days of the week. A simple example might look something like:
In this example, ‘x’ changes depending on what day it is. When the program is executed, it will determine the current day of the week and then print the result on the screen. ‘x’ is the variable in the program.
When you take an algebra class, the most commonly used variables are ‘x’, ‘y’, and ‘z’, but any letters can be used.
One advantage of using variables is when the same variable is used multiple times in a single expression or equation. When this happens, the variable will always have the same value throughout the expression or equation which makes operations like canceling, combining, adding, subtracting, etc., possible (and easy to do).
Because we most often use the variable ‘x’, it would be confusing to also use the letter ‘x’ to denote multiplication so other notations have been created. The following are all equivalent ways of representing ‘x’ multiplied by ‘x’.
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