Math Problem Statement

Prove by induction that 2^n > n for all n in N (natural numbers).

Solution

The problem asks to prove by induction that 2n>n2^n > n for all nNn \in \mathbb{N} (the set of natural numbers).

Step-by-step proof using induction:

Base Case (n = 1):

We first check if the inequality holds for n=1n = 1. 21=2andn=1.2^1 = 2 \quad \text{and} \quad n = 1. Clearly, 2>12 > 1, so the base case is true.

Induction Hypothesis:

Assume that for some n=kn = k, the inequality holds, i.e., 2k>k.2^k > k. This is the induction hypothesis.

Induction Step:

We need to prove that if the inequality holds for n=kn = k, then it also holds for n=k+1n = k + 1. That is, we need to show that: 2k+1>k+1.2^{k+1} > k+1.

Starting with the left-hand side: 2k+1=22k.2^{k+1} = 2 \cdot 2^k. By the induction hypothesis, we know that 2k>k2^k > k, so: 2k+1=22k>2k.2^{k+1} = 2 \cdot 2^k > 2 \cdot k. Thus, we now need to show that 2kk+12k \geq k + 1. Simplifying this inequality: 2kk+1k1.2k \geq k + 1 \quad \Longleftrightarrow \quad k \geq 1. This is true for all k1k \geq 1.

Therefore, the induction step holds, and by the principle of mathematical induction, we have proven that 2n>n2^n > n for all nNn \in \mathbb{N}.


Would you like further details or clarifications? Here are some related questions:

  1. What is the principle of mathematical induction and why is it useful?
  2. Can you apply this induction method to other exponential functions, like 3n>n23^n > n^2?
  3. What happens if we test the inequality 2nn2^n \geq n for n=0n = 0?
  4. How does the inequality 2n>n2^n > n behave as nn becomes very large?
  5. How do we modify the proof if nZ+n \in \mathbb{Z^+} (positive integers)?

Tip: Inductive proofs often work well when the statement to be proved involves recursive or iterative structures.

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Math Problem Analysis

Mathematical Concepts

Mathematical Induction
Inequalities
Exponents

Formulas

2^n > n

Theorems

Principle of Mathematical Induction

Suitable Grade Level

Undergraduate or Advanced High School