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If the sum of the first $14$ terms of an A.P. is $1050$ and the first term is $10$, then find the $20^{\text{th}}$ term and the $n^{\text{th}}$ term.
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$\frac{14}{2}(20 + 13d) = 1050$
$\Rightarrow d = 10$
$\therefore a_{20} = 10 + 19 \times 10 = 200$
$a_n = 10 + (n - 1) 10 = 10n$
$\Rightarrow d = 10$
$\therefore a_{20} = 10 + 19 \times 10 = 200$
$a_n = 10 + (n - 1) 10 = 10n$