Question

use the following function rule to find f(81).
$f(x) = 2\sqrt{x}$
$f(81) = \square$

Explanation:

Step1: Substitute $x=81$ into $f(x)$

$f(81) = 2\sqrt{81}$

Step2: Calculate square root of 81

$\sqrt{81} = 9$

Step3: Multiply to get final value

$f(81) = 2 \times 9$

Answer:

18