Recurrence Relations

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1. solution Find the limiting ratio \lim_{n\rightarrow\infty} \frac{x_{n+1}}{x_n}\, for the recurrence relation x_n=x_{n-1}+x_{n-2}\,.

2. solution Let x_n := \left\{\begin{matrix}
x_{n-1} + x_{n-2} & \mbox{if } n>1  \\
x_1 \in \mathbb{N} & \mbox{if } n=1 \\
x_0 \in \mathbb{N} & \mbox{if } n=0 \\
0 & \mbox{if } n<0 \end{matrix}\right.
Show that x_n = x_{1}F_{n-1} + x_{0}F_{n-2} \,\! where F_n\,\! is the n-th Fibonacci number   (F0 = F1 = 1)

3. solution Let x_n := \left\{\begin{matrix}
1+\frac{1}{x_{n-1}} & \mbox{if } n>0  \\
x_0 \in \mathbb{N} & \mbox{if } n=0  \\
0 & \mbox{if } n<0 \end{matrix}\right.
Show that x_n = \frac{x_{0}F_{n} + F_{n-1}}{x_{0}F_{n-1} + F_{n-2}} \,\! where F_n\,\! is the n-th Fibonacci number   (F0 = F1 = 1 and F(n < 0) = 0)

4. solution Let x_n := \left\{\begin{matrix}
x_{n-1}*x_{n-2} & \mbox{if } n>1  \\
x_1 \in \mathbb{N} & \mbox{if } n=1  \\
x_0 \in \mathbb{N} & \mbox{if } n=0  \\
0 & \mbox{if } n<0 \end{matrix}\right.
Show that x_n = x_{1}^{F_{n}}*x_{2}^{F_{n-1}} \,\! where F_n\,\! is the n-th Fibonacci number   (F0 = F1 = 1 and F(n < 0) = 0)

5. solution Let x_n := \begin{cases}
a + x_{n/c} & \mbox{if } n>1 \\
b & \mbox{if } n\le1\end{cases}\mbox{ }c>1,\mbox{ }n,c \in \mathbb{R}
Evaluate x_n\,\!.

6. solution Let x_n := \begin{cases}
\frac{1 + n! * x_{n-1}}{n*n!} & \mbox{if } n > 0 \\
0 & \mbox{otherwise}\end{cases} \,\!
Show that x_n = \frac{1}{n!}\sum_{i=1}^{n} \frac{1}{i}\,\!.

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