10. (i) A sequence of numbers \(u _ { 1 } , u _ { 2 } , u _ { 3 } , \ldots\), is defined by $$u _ { n + 1 } = 5 u _ { n } + 3 , \quad u _ { 1 } = 3$$ Prove by induction that, for \(n \in \mathbb { Z } ^ { + }\), $$u _ { n } = \frac { 3 } { 4 } \left( 5 ^ { n } - 1 \right)$$ (ii) Prove by induction that, for \(n \in \mathbb { Z } ^ { + }\), $$f ( n ) = 5 \left( 5 ^ { n } \right) - 4 n - 5 \text { is divisible by } 16 .$$ \includegraphics[max width=\textwidth, alt={}, center]{9093bb1d-4f32-44e7-b0e7-b8c4f8a844e1-32_109_127_2473_1818}
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