Math Problem Statement

√n+1 -√n write the first fout elements of the sequence and determine whether it is convergent or divergent (substitute n to 1, 2, 3 and 4)

Solution

Let's consider the expression n+1n\sqrt{n+1} - \sqrt{n} and compute the first four terms of the sequence by substituting n=1,2,3,4n = 1, 2, 3, 4:

  1. For n=1n = 1: 1+11=21=211.4141=0.414\sqrt{1+1} - \sqrt{1} = \sqrt{2} - \sqrt{1} = \sqrt{2} - 1 \approx 1.414 - 1 = 0.414

  2. For n=2n = 2: 2+12=321.7321.414=0.318\sqrt{2+1} - \sqrt{2} = \sqrt{3} - \sqrt{2} \approx 1.732 - 1.414 = 0.318

  3. For n=3n = 3: 3+13=43=21.732=0.268\sqrt{3+1} - \sqrt{3} = \sqrt{4} - \sqrt{3} = 2 - 1.732 = 0.268

  4. For n=4n = 4: 4+14=542.2362=0.236\sqrt{4+1} - \sqrt{4} = \sqrt{5} - \sqrt{4} \approx 2.236 - 2 = 0.236

Thus, the first four terms of the sequence are approximately: 0.414,0.318,0.268,0.2360.414, \, 0.318, \, 0.268, \, 0.236

Convergence or Divergence:

As nn \to \infty, both n+1\sqrt{n+1} and n\sqrt{n} grow large, but the difference between them becomes smaller. More precisely:

n+1n=(n+1n)(n+1+n)n+1+n=1n+1+n\sqrt{n+1} - \sqrt{n} = \frac{(\sqrt{n+1} - \sqrt{n})(\sqrt{n+1} + \sqrt{n})}{\sqrt{n+1} + \sqrt{n}} = \frac{1}{\sqrt{n+1} + \sqrt{n}}

As nn \to \infty, the denominator n+1+n\sqrt{n+1} + \sqrt{n} grows large, making the entire expression approach 0. Therefore, the sequence converges to 0.

Conclusion:

The sequence is convergent.

Would you like further details or have any questions?


Here are 5 related questions to expand your understanding:

  1. What is the general form of the limit for sequences involving square roots?
  2. How can you prove the convergence of a sequence using mathematical limits?
  3. What happens if you try this with a different form, like n+2n\sqrt{n+2} - \sqrt{n}?
  4. How would the sequence behave if nn starts at 0 instead of 1?
  5. How can we approximate the difference n+1n\sqrt{n+1} - \sqrt{n} for large nn?

Tip: In sequences involving square roots, rationalizing the expression often helps in determining convergence properties!

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Math Problem Analysis

Mathematical Concepts

Sequences
Limits
Square Roots

Formulas

√(n+1) - √n
Limit of a sequence as n → ∞

Theorems

Convergence of sequences

Suitable Grade Level

Grades 10-12