### 2.24.9 Factorize *x*^{n} in a polynomial : `factor_xn`

`factor_xn` takes as argument a polynomial `P`.

`factor_xn` returns the polynomial `P` written
as the product of it’s monomial of largest degree *x*^{n} (`n=degree(P)`)
with a rational fraction having a non-zero finite limit at infinity.

Input :

`factor_xn(-x``^`

`4+3)`

Output :

`x``^`

`4*(-1+3*x``^`

`-4)`