Exercise · ZW-CONVERGENT-OF-A-CONTINUED-FRACTION-002 · ★☆☆ Basic

What is the value of \( q_1 \) for the continued fraction \( [2;5,4] \)?

Choose one option.

Show answer
  • D. \( 5 \)

Explanation

With \( q_{-1}=0 \) and \( q_0=1 \), we have \( q_1=a_1q_0+q_{-1}=5 \). The option with value \( 11 \) results from adding \( a_0 \) and \( a_1 \) instead of using the recurrence.

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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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