The cube of the difference of two expressions  is equal to the cube of the first minus three times the product of the square of the first and the second minus the cube of the second.

 

The cube of the difference of two expressions

Important!

 

The cube of the difference

Derivation of the formula of the cube of the difference

Derivation of the formula of the cube of the difference

How to memorise the cube of the difference formula

 

In order to memorise the arrangement of signs in the cube of the difference formula, then it is necessary to put the “+” sign before the first a3 and then alternate “+” and “-“: i.e. at first “+”, then “-“, then again “+”, then again “-“:

The cube of the difference of two expressions