2014-II-14 – Solving Master

Ans: D
By the given formula, we have

${\begin{cases} a_{5} = a_{4} + a_{3} & \dots ① \\ a_{4} = a_{3} + a_{2} & \dots ② \end{cases}$

$① - ②$ , we have

$\begin{array}{rcl} a_{5} - a_{4} & = & (a_{4} + a_{3}) - (a_{3} + a_{2}) \\ a_{5} - a_{4} & = & a_{4} - a_{2} \\ a_{5} & = & 2 a_{4} - a_{2} \\ a_{5} & = & 2 (63) - 7 \\ a_{5} & = & 119 \end{array}$

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