Limits Calculation
1. Problem a: Find $$\lim_{n \to \infty} \sqrt[n]{5n + 3}.$$
We rewrite as $$ (5n+3)^{1/n} = e^{\frac{1}{n} \ln(5n+3)}.$$
As $$n \to \infty$$, $$\frac{\ln(5n+3)}{n} \to 0$$ since $$\ln(n)$$ grows slower than $$n$$.
Thus, the limit is $$e^0 = 1.$$
2. Problem б: $$\lim_{n \to \infty} \left( \sqrt[n]{2n + 1} + \sqrt[n]{100} \right).$$
We use the same logic: $$\sqrt[n]{2n + 1} \to 1$$ and $$\sqrt[n]{100} = 100^{1/n} \to 1.$$
Sum limit is $$1 + 1 = 2.$$
3. Problem в: $$\lim_{n \to \infty} \frac{\sqrt[n]{n^4} + \sqrt[n]{5}}{6 \sqrt[n]{n^3} + \sqrt[n]{2}}.$$
Rewrite terms: $$\sqrt[n]{n^k} = e^{\frac{k}{n} \ln n} \to e^0 = 1$$ and $$\sqrt[n]{\text{const}} \to 1.$$
Numerator $$\to 1 + 1 = 2$$ and denominator $$\to 6 \cdot 1 + 1 = 7.$$
Limit is $$\frac{2}{7}.$$
4. Problem г: $$\lim_{n \to \infty} \frac{3^n + 7^n}{3^{n+2} + 7^{n+2}}.$$
Since $$7^n$$ dominates numerator and denominator, factor $$7^n$$:
Numerator $$= 7^n (\frac{3^n}{7^n} + 1) = 7^n \left(\left(\frac{3}{7}\right)^n + 1\right)$$,
Denominator $$= 7^{n+2} \left(\left(\frac{3}{7}\right)^{n+2} + 1\right) = 7^2 \cdot 7^n \left(\left(\frac{3}{7}\right)^{n+2} + 1\right).$$
Cancel $$7^n$$: limit is $$\frac{ (\frac{3}{7})^n + 1 }{ 49 \left( (\frac{3}{7})^{n+2} + 1 \right) } \to \frac{1}{49}$$ since $$\left(\frac{3}{7}\right)^n \to 0.$$
5. Problem д: $$\lim_{n \to \infty} \left( 1 + \frac{2}{n} \right)^{3n}.$$
Rewrite as $$\left[ \left(1+\frac{2}{n}\right)^n \right]^3$$, limit of $$\left(1 + \frac{2}{n}\right)^n$$ is $$e^2$$, so whole expression tends to $$\left(e^2\right)^3 = e^6.$$
6. Problem ґ: $$\lim_{n \to \infty} \left( \frac{5n^3 + 2}{5n^3} \right)^{\sqrt{n}} = \lim_{n \to \infty} \left( 1 + \frac{2}{5n^3} \right)^{\sqrt{n}}.$$
Since $$\frac{2}{5n^3} \to 0$$ very fast and $$\sqrt{n}$$ grows slower, limit of exponent $$\sqrt{n} \cdot \frac{2}{5n^3} = \frac{2}{5} n^{-5/2} \to 0.$$
Hence, limit is $$e^0 = 1.$$
7. Problem е: $$\lim_{n \to \infty} \left( \frac{n^2 + 2}{n^2 + 1} \right)^{n^2} = \lim_{n \to \infty} \left( 1 + \frac{1}{n^2 + 1} \right)^{n^2}.$$
Rewrite as $$\exp\left(n^2 \ln\left(1 + \frac{1}{n^2 + 1}\right)\right).$$
For large $$n$$, $$\ln(1+x) \approx x$$, so the exponent tends to $$n^2 \cdot \frac{1}{n^2+1} \to 1.$$
Limit is $$e^1 = e.$$
8. Problem ж: $$\lim_{n \to \infty} \left(1 + \frac{1}{n}\right)^{\frac{n + 1}{n}} = \lim_{n \to \infty} \left(1 + \frac{1}{n}\right)^{1 + \frac{1}{n}}.$$
Split exponent: $$= \lim_{n \to \infty} \left(1 + \frac{1}{n}\right) \cdot \left(1 + \frac{1}{n}\right)^{1/n}.$$
First part tends to 1, second tends to $$e^0 = 1$$, so product tends to $$1.$$
Wait, check carefully:
Actually, $$\left(1 + \frac{1}{n}\right)^n \to e$$, so $$\left(1 + \frac{1}{n}\right)^{\frac{n + 1}{n}} = \left( (1+\frac{1}{n})^n \right)^{1/n + 1/n^2}$$ which tends to $$e^{1 + 0} = e.$$
Hence, limit is $$e.$$
9. Problem з: $$\lim_{n \to \infty} \frac{(2n)!! + (2n + 2)!!}{(n^2 + 1)(2n - 2)!!}.$$
Use double factorial relation: $$ (2n)!! = 2^n n!$$ for even double factorial. Similarly, approximate growth; numerator dominated by $$ (2n+2)!! = (2n+2)(2n)!!$$.
Rewrite numerator as $$ (2n)!! (1 + 2n + 2) \text{ (dominant term)}.$$
Denominator: $$ (n^2 + 1) (2n-2)!! \approx n^2 (2n)!!/ (2n) $$ by shifting factors. Detail yields limit tending to infinity since numerator grows faster.
More precise calculation yields limit diverges to infinity.
10. Problem s: $$\lim_{n \to \infty} \frac{a^n + 3b^n}{a^{n-1} + b^{n+2}}, \quad b>a>0.$$
Since $$b > a$$, $$b^n$$ dominates numerator and denominator. Write numerator as $$b^n\left( \left(\frac{a}{b}\right)^n + 3 \right) \to 3b^n,$$ denominator as $$b^{n+2}\left( \left(\frac{a}{b}\right)^{n-1} + 1 \right) \to b^{n+2}.$$
Limit is $$\frac{3b^n}{b^{n+2}} = \frac{3}{b^2}.$$
Final answers summarized:
a) 1
б) 2
в) 2/7
г) 1/49
д) $$e^6$$
ґ) 1
е) $$e$$
ж) $$e$$
з) diverges (infinity)
s) $$\frac{3}{b^2}$$