Question

Write the explicit
rule for the nth term.
Then find a21
{4, 16, 64...}

Answer 1

The rule would be 4ⁿ

4²¹

Explanation:

This is a geometric sequence, the terms are all powers of 4.

The rule here would be 4ⁿ

To find the 21st term, we simply substitute 21 for n in our rule. So:

= 4²¹

Leaving in index form is fine as the expanded number is very large