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Answers for “如何通过数学归纳法证明 $a_n \ge \frac{1}{2}$?”

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The proof uses mathematical induction. First, the base case is verified by checking that a1=1≥12a_1=1 \ge \frac{1}{2}.

Conditions: The sequence is defined by an+1=13(an+1)a_{n+1}=\frac{1}{3}(a_n+1) for n≥1n \ge 1.; The initial value is a1=1a_1=1.; The goal is to prove an≥12a_n \ge \frac{1}{2} for all n≥1n \ge 1.

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To compute the terms, substitute the initial value into the recurrence relation iteratively. First, plug in a1=1a_1=1 to find a2a_2.

Conditions: The recurrence relation is an+1=13(an+1)a_{n+1}=\frac{1}{3}(a_n+1).; The initial value is a1=1a_1=1.; The index nn starts at 11.