So why are we using ** x**‘s and

**y**‘s,

*and other letters*, now in maths? Shouldn’t we be using numbers in maths? Well. Sometimes we don’t actually know the value of those numbers. Or the value could be anything –

*any real number*.

Think of ** x** just as a

**container**, or some means of

*holding onto*some number (which we may or may not know). This is helpful as we can now do mathematical operations to this ‘mystery number’.

The fancy term people like to use to describe the container ** x**, is a

**variable**.

Usually we have two types of variables; an *independent*** variable** and a *dependent*** variable**. If a variable is independent, then it can (usually) take on any real number value. If a variable is dependent, then the value of this variable DEPENDS on another variable.

(If the last paragraph went over your head – that’s okay, just remember that *x* is a ‘**container**’ and this is synonymous with the word ‘**variable**’).

Let me give you an example of an *independent* & *dependent* variable:

`y = x+5`

This is an equation – *and depending on how far you are into algebra, you may recognise this as a straight line* – think of this equation as a **machine** like so:

This diagram suggests that; “*Input **x** and the machine will spit out output ** y*“.

Now, you can see that the * y* value

*depends*on the

*value. And the*

**x***value could by anything (i.e*

**x***Independent*).

We usually see ** x**‘s and

*‘s thrown around in algebra, but in reality we could use any letter or symbol (even a shape, and*

**y***sometimes*even a letter from the greek alphabet).

See: Greek letters used in mathematics, science, and engineering – Wikipedia

Still stuck understanding *x*‘s and *y*‘s, and the difference between a **dependant variable** and an **independent variable**? Perhaps a video might help: