If you were to multiply numerator and denominator out, they would be polymnomials of degree 6 with leading term (you don't have to actually multiply to see that). If you divide both numerator and denominator by , each will be 1+ terms with u in the denominator. As u goes to either positive or negative infinity the terms with u in the denominator go to 0 so, yes, the whole fraction goes to 1/1= 1.