What is the proof for a^n > n for all natural numbers n and a >= 2?

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Homework Help Overview

The discussion revolves around proving the inequality \( a^n > n \) for all natural numbers \( n \) and \( a \geq 2 \). Participants are exploring the implications of a previously established result involving the binomial theorem and induction.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss using induction to prove the inequality, with one member expressing confusion about the term "deduce" and seeking clarity on how to connect their previous proof to the current problem.
  • There is an exploration of setting \( a = 1 + x \) and questioning how this relates to the condition \( a \geq 2 \).
  • Another participant attempts to derive \( a^n \geq 1 + nx \) and considers the implications of \( n \) being a natural number.

Discussion Status

The discussion is ongoing, with participants providing guidance and clarifications. There is an acknowledgment of the need to connect previous results to the current proof, and some participants are exploring different interpretations of the problem without reaching a consensus.

Contextual Notes

Participants are navigating the definitions and implications of the terms used in the problem, particularly regarding the conditions for \( a \) and \( n \). There is also a focus on the assumptions underlying the use of induction in their reasoning.

synkk
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Prove for all ## x \geq -1 ## and n being a natural number, ## (1+x)^n \geq 1 + nx ## I've done this using induction

hence deduce from this that for any real number # a \ geq 2 ##, ## a^n > n ## for all n belonging to the natural numbers.

I'm stuck at the deduce part

I'm not sure what deduce means, it seems fairly obvious so instead I tried to prove it, by again, induction:

a = 2,
2^n > n which is true a n >= 1
assume true for a = k

then when a = k+1

(k+1)^n > n

I don't see how I can prove it from here, it seems obvious as k >= 2 and n >=1 this will always hold true, and thus a^n > n but I can't seem to prove it. Does anyone have any tips on proving as I'm fairly new at this

thank you
 
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synkk said:
Prove for all ## x \geq -1 ## and n being a natural number, ## (1+x)^n \geq 1 + nx ## I've done this using induction

hence deduce from this that for any real number # a \ geq 2 ##, ## a^n > n ## for all n belonging to the natural numbers.

I'm stuck at the deduce part

I'm not sure what deduce means

It means "show that this follows from what you have just proved".

In this case, you've shown that if [itex]x \geq -1[/itex] then [itex](1 + x)^n \geq 1 + nx[/itex].

Now see what happens if you set [itex]a = 1 + x[/itex].
 
pasmith said:
It means "show that this follows from what you have just proved".

In this case, you've shown that if [itex]x \geq -1[/itex] then [itex](1 + x)^n \geq 1 + nx[/itex].

Now see what happens if you set [itex]a = 1 + x[/itex].

how would that work exactly? it states that a >= 2 if we let a = 1 + x then a >= 0 as x >= -1?
 
Last edited:
if I ignore my confusion above I ge tthis:

a^n >= 1 + nx

as x >= -1 a^n >= 1 - n

as n is a natural number n >=1
hence a^n > n
 

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