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.
 

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

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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