Find the general formula for the arithmetic sequence below. Without using a recursive formula, calculate the ${30}^{\mathrm{th}}$ term.
$\{-9,-4,1,6,\dots \}$

In the sequence 21,700, 23,172, 24,644, 26,116,... which term is 314,628?

Show that the sum of the first n positive odd integers,1 +3 +5 + ··· + (2n − 1), ... is n².

Use the formula $a_n=4+(n-1)(-7)$ to find the eighth term of the sequence $4,-3,-10,\dots$

Write a recursive formula for the arithmetic sequence.

$\{8,2,-4,-10,\dots \}$