### 2.12.5 Distributivity : `expand fdistrib`

`expand` or `fdistrib` takes as argument an expression.

`expand` ou `fdistrib` returns the expression where the distributivity
of the multiplication with respect to the addition is applied.

Input :

`expand((x+1)*(x-2))`

Or :

`fdistrib((x+1)*(x-2))`

Output :

`x``^`

`2-2*x+x-2`