# Tagged Questions

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### Proving $4^n > n^4$ holds for $n\geq 5$ via induction.

I know that it holds for $n=5$, so the first step is done. For the second step, my IH is: $4^n > n^4$, and I must show that $4^{n+1} > (n+1)^4$. I did as follows: $4^{n+1} = 4*4^n > 4n^4$, ...
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### Prove or Disprove Inequality By Induction

Prove or Disprove $\sum_{i=0}^n(2i)^3 \le (8n)^3$ If true, prove using induction. If false, give the smallest value of n that is a counter example and the values for the left and right hand sides ...
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### Proving that if $n>2$ then $n!>n^{n/2}$ using induction. [duplicate]

How to prove that if $n>2$ then $n!>n^{n/2}$ using induction?
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### Proof an inequality by mathematical induction

I have a problem that I have to solve using mathematical induction but I'm stuck from a part. The problem is: Proof that $\large n<2^n$ is true for $\large n \in \mathbb{N}\$ So, I did that ...
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### Need to prove inequality $\sum\limits_{k=0}^n \frac{1}{(n+k)} \ge \frac{2}{3}$

Prove that for $n \geq 1$: $$\sum\limits_{k=0}^n \frac{1}{(n+k)} \ge \frac{2}{3}$$ I have tried math induction but that didn't work. Although I'm pretty sure that the solving can be done by induction ...
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### Prove $1! + 2! + . . . + n! < (n + 1)!$ using mathematical induction [duplicate]

$1! + 2! + . . . + n! < (n + 1)!$ This question has left me stumped for quite some time. I am not sure how to approach it. (I am really bad at induction).
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### how to prove $1/n (1-(1/2)^n)$ decreasing without using differentiation

$a(n)=1/n (1-(1/2)^n)$ prove $a(n+1)<a(n)$ for n>0 by differentiating slope comes negative and then we can prove it . but i wanted to solve it without that . can someone help
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### Induction inequality on sum of reciprocals

I have to prove that: $\displaystyle\frac{1}{n}+\frac{1}{n+1}+...+\frac{1}{2n}\ge\frac{1}{2}$ for natural $n$ Checking for $n=1$ we have $\displaystyle 1+\frac{1}{2}=\frac{3}{2}\ge \frac{1}{2}$ ...
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### Prove that $\sqrt{n} \le \sum_{k=1}^n \frac{1}{\sqrt{k}} \le 2 \sqrt{n} - 1$ is true for $n \in \mathbb{N}^{\ge 1}$

I'm trying to solve these induction exercises proposed by the department of mathematics of Oxford University. I don't know how to give a valid proof for the third one which says the following: ...
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### Prove $\forall n \in\Bbb N$, $0 < a < 1$ $\implies$ $a^n \leq 1$

I'm trying to prove this by induction but I'm running into some trouble. The base case is $0$, so, $a^0 = 1$, the inequality holds true Being new to induction, I don't exactly know what to do for ...
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### Proving inequality $3^{n^2} > (n!)^4$

Prove that $3^{n^2} > (n!)^4$ for all positive integers $n$. I tried to use induction on this problem but failed to do so. I instead tried to prove $3^{2n+1}>(n+1)^4$, but couldn't come up ...
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### I can prove that the series is greater than $\frac{1}{2}$ however i can't prove that it is greater than $\frac{13}{24}$ [duplicate]

Prove that for any positive integer $n>1$ $$\frac{1}{n+1} + \frac{1}{n+2} + \frac{1}{n+3} \ldots + \frac{1}{2n} > \frac{13}{24}$$ I can prove that the series is greater than $\frac{12}{24}$ ...
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### Prove $x_n \leq x_{n+1}$ for all $n$ by induction

Prove $x_n \leq x_{n+1}$ for all $n$ by induction. I am reading this example from "Understanding Analysis" by Abbott (page 10). He says the multiple across the inequality by $1/2$ and then add 1 to ...
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### Induction: show that $\sum\limits_{k=1}^n \frac{1}{\sqrt{k}} < 2 \sqrt{n}$ for all n $\in Z_+$
The question: show by using induction that $\sum\limits_{k=1}^n \frac{1}{\sqrt{k}} < 2 \sqrt{n}$ for all n $\in Z_+$ My attempt at a solution: The base case $n = 1$ is true. First we use the ...
### Prove $2^n\cdot n! ≤ (n+1)^n$ by induction.
An induction I'm struggling with. Prove $2^n\cdot n! ≤ (n+1)^n$ by induction. An idea was to show that $2^n\cdot n! ≤ 1+n^2$ since $1+n^2 ≤ (n+1)^n$ using Bernoulli. However the inequality is ...