Limit Factorial D8F2B5
1. Muammo: Quyidagi limitni hisoblang:
$$\lim_{n \to \infty} \frac{n^n}{\left[(n+1)!\right]^2}$$
2. Formulalar va qoidalar: Faktorial ta'rifi \( (n+1)! = 1 \cdot 2 \cdot 3 \cdots (n+1) \) va limitni hisoblashda Stirling formulasi yoki taqqoslash usullaridan foydalanish mumkin.
3. Hisoblash:
\( (n+1)! = (n+1) \cdot n! \), shuning uchun
$$\left[(n+1)!\right]^2 = ((n+1)!)^2 = (n+1)^2 (n!)^2$$
4. Shunday qilib, ifoda:
$$\frac{n^n}{((n+1)!)^2} = \frac{n^n}{(n+1)^2 (n!)^2}$$
5. Endi \(n!\) ni Stirling formulasiga yaqinlashtiramiz:
$$n! \approx \sqrt{2 \pi n} \left(\frac{n}{e}\right)^n$$
6. Shunday qilib,
$$ (n!)^2 \approx 2 \pi n \left(\frac{n}{e}\right)^{2n} $$
7. Ifodani almashtiramiz:
$$\frac{n^n}{(n+1)^2 \cdot 2 \pi n \left(\frac{n}{e}\right)^{2n}} = \frac{n^n}{(n+1)^2 \cdot 2 \pi n} \cdot \frac{e^{2n}}{n^{2n}} = \frac{e^{2n}}{(n+1)^2 \cdot 2 \pi n} \cdot \frac{n^n}{n^{2n}}$$
8. Soddalashtiramiz:
$$\frac{n^n}{n^{2n}} = n^{-n}$$
Shunday qilib,
$$\frac{e^{2n}}{(n+1)^2 \cdot 2 \pi n} \cdot n^{-n} = \frac{e^{2n}}{(n+1)^2 \cdot 2 \pi n} \cdot \frac{1}{n^n}$$
9. Limitga qarasak, \(n^n\) juda tez o'sadi, shuning uchun \(\frac{1}{n^n} \to 0\) juda tez kamayadi va butun ifoda 0 ga yaqinlashadi.
10. Natija:
$$\lim_{n \to \infty} \frac{n^n}{\left[(n+1)!\right]^2} = 0$$
Bu limit 0 ga teng.