Answer
$84=(6)(14)$
Work Step by Step
$84=$
...write $84$ as a difference of two squares.
$=100-16$
...write each term as a square.
$=10^{2}-4^{2}$
...use the rule for the difference of two squares.
$=(10-4)(10+4)$
...simplify.
$=(6)(14)$