### 5.25.9 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 its 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)