Separation of variables : split

### 2.12.8 Separation of variables : `split`

`split` takes two arguments : an expression depending on two variables and the list of these two variables.
If the expression may be factorized into two factors where each factor depends only of one variable, `split` returns the list of this two factors, otherwise it returns the list `[0]`.
Input :

`split((x+1)*(y-2),[x,y])`

Or :

`split(x*y-2*x+y-2,[x,y])`

Output :

`[x+1,y-2]`

Input :

`split((x```^```2*y```^```2-1,[x,y])`

Output :

`[0]`