Question

Which term is correct when simplifying √128?

A.) 16
B.) 12
C.) 10
D.) 8√2

Answer 1

when dealing with roots, we want to factor to see if it's possible

$128 = 2 \times 64$
$= 2 \times 2 \times 32$
$= 2 \times 2 \times 2 \times 16$
$= 2 \times 2 \times 2 \times 2 \times 8$
$= 2 \times 2 \times 2 \times 2 \times 2 \times 4$
$= 2 \times 2 \times 2 \times 2 \times 2 \times 2 \times 2$

now since we're dealing with square roots, we circle every pair of numbers we see in the final factoring
so..
$= (2 \times 2) \times (2 \times 2) \times (2 \times 2) \times 2$

now for every circled pair, we take only 1 of the 2 circled and bring it outside
anything left uncircled stays inside the root
so..
$= 2 \times 2 \times 2 \times \sqrt{2}$

now simply multiply
$8 \sqrt{2}$