When does the sequence generated by the Babylonian method converge to the square root of a?
Conditions
- The constant .
- The initial guess .
- The limit is taken as .
Reasoning, step by step
- Verify that and .
- Apply the Arithmetic Mean-Geometric Mean (AM-GM) inequality to show that for all .
- Demonstrate that the sequence is monotone decreasing for (since when ).
- Invoke the Monotone Convergence Theorem to assert that the limit exists.
- Let .
- Solve the equation to find (discarding the negative root).
- Conclude that the sequence converges to as .
Example
The video states: 'given and the recursive formula... prove that the limit of the sequence exists as n approaches infinity, and find this limit.' The solution involves proving monotonicity and boundedness.
Common misconceptions
- Believing that the sequence converges for any real initial guess, including negative ones.
- Thinking that the convergence is immediate after one step.
- Confusing the existence of the limit with the value of the limit.
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