Arithmetical operations

A casual math expression that contains basic arithmetical operations has the same view in TeX language as in a casual text. For example:

(x+y)a - (x+y)b = (x+y)(a-b)

This example illustrates that addition, subtraction and equality use the following symbols: '+', '-' and '='. '(' and ')' are used for the parentheses.

The math rule that allows of omitting a multiplication sign also works in TeX. When it leads to ambiguity (for example, multiplication of numbers) it is necessary to use the '\cdot' command.

2 \cdot 6 = 12

A space is a marker of the command's end. It can be omitted when after one command the other command starts immediately, or when the parentheses ('{', '}', '(', ')') or the other special symbols ('_', '^') are mentioned right after the command. The other space property is that it hasn't any functions beside the command's end marker, so spaces can be mentioned anywhere (except commands) in the formula without any visible effects.

Enter the representation of the following formula in TeX format to test yourself: