Exercise · ZW-CONVERGENT-OF-A-CONTINUED-FRACTION-003 · ★☆☆ Basic

What is the convergent \( p_1/q_1 \) of \( [0;1,2,3] \)?

Choose one option.

Show answer
  • C. \( 1/1 \)

Explanation

Since \( p_1=a_1p_0+p_{-1}=1\cdot 0+1=1 \) and \( q_1=1 \), the convergent is \( 1/1 \). The option \( 0/1 \) is the zeroth convergent, not the first one.

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Review the concept: Convergent of a continued fraction

A convergent of a continued fraction \( [a_0; a_1, a_2, \ldots] \) is the rational number \( p_n/q_n \) obtained by truncating the expansion at the term \( a_n \).

\[\frac{p_n}{q_n}=[a_0;a_1,\ldots,a_n],\quad p_n=a_np_{n-1}+p_{n-2},\\q_n=a_nq_{n-1}+q_{n-2}\]

More practice problems: convergent of a continued fraction

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