Proving Inequality with Bernoulli's: k≤n Positive Integers

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In summary, to show that \left (1+\frac1 n \right)^k \leq 1 + \frac{ke}{n}, we can use Bernoulli's inequality and some basic results from calculus. By noting that \left( 1 + \frac{1}{n} \right)^n is monotonically increasing to e, we can simplify the inequality to e^{\frac{k}{n}} \leq 1 + \frac{ke}{n}. By setting a = k/n \leq 1 and rearranging the inequality, we can show that \frac{ e^a - e^0 }{ a- 0} \leq e, which follows from the
  • #1
bennyzadir
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Let be [tex] k \leq n [/tex] poitive integers. How to show that
[tex]\left (1+\frac1 n \right)^k \leq 1 + \frac{ke}{n} [/tex] .

It seems to me that it has something to do with Bernoulli's inequality.
Thank you in advance!
 
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  • #2
Are you allowed to use some basic results from calculus for this problem? Note that [tex] \left( 1 + \frac{1}{n} \right)^n [/tex] is monotonically increasing to e, so [tex] \left( 1 + \frac{1}{n} \right)^k = \left(\left( 1 + \frac{1}{n} \right)^n\right)^{\frac{k}{n}} < e^{\frac{k}{n}} [/tex]. Thus it is sufficient to show that [tex] e^{\frac{k}{n}} \leq 1 + \frac{ke}{n} [/tex]. Let [itex] a= k/n \leq 1 [/itex]. Then rearranging the required inequality, we have to show [tex] \frac{ e^a - e^0 }{ a- 0} \leq e [/tex], which follows quite quickly from the Mean Value Theorem.
 
  • #3
Gib Z said:
Are you allowed to use some basic results from calculus for this problem? Note that [tex] \left( 1 + \frac{1}{n} \right)^n [/tex] is monotonically increasing to e, so [tex] \left( 1 + \frac{1}{n} \right)^k = \left(\left( 1 + \frac{1}{n} \right)^n\right)^{\frac{k}{n}} < e^{\frac{k}{n}} [/tex]. Thus it is sufficient to show that [tex] e^{\frac{k}{n}} \leq 1 + \frac{ke}{n} [/tex]. Let [itex] a= k/n \leq 1 [/itex]. Then rearranging the required inequality, we have to show [tex] \frac{ e^a - e^0 }{ a- 0} \leq e [/tex], which follows quite quickly from the Mean Value Theorem.

Thank you very much for your clear and understandable answer.
 

1. What is Bernoulli's inequality and how does it relate to proving inequality with positive integers?

Bernoulli's inequality states that for any real number x greater than or equal to -1 and any positive integer n, (1+x)^n ≥ 1+nx. This inequality can be used to prove other inequalities involving positive integers, such as k≤n.

2. Can Bernoulli's inequality be used to prove all types of inequalities involving positive integers?

No, Bernoulli's inequality is limited to proving inequalities where k≤n and may not be applicable to other types of inequalities involving positive integers.

3. How does one use Bernoulli's inequality to prove k≤n for positive integers?

To prove k≤n using Bernoulli's inequality, one can assume that k≤n is true and then apply Bernoulli's inequality to the expression (1+x)^n, where x is a positive integer. This will result in a statement that is equivalent to k≤n, thus proving the inequality.

4. Are there any limitations to using Bernoulli's inequality to prove k≤n for positive integers?

Yes, Bernoulli's inequality can only be used to prove k≤n for positive integers if the exponent n is a positive integer itself. If n is not a positive integer, then Bernoulli's inequality cannot be applied.

5. Can Bernoulli's inequality be used to prove other types of inequalities besides k≤n for positive integers?

Yes, Bernoulli's inequality can be used to prove other types of inequalities, such as k^n ≥ n^k, where k and n are positive integers. However, it is important to keep in mind the limitations of this inequality and consider if it is applicable to the specific inequality being proven.

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