Answer
$49h^{2}-4$
Work Step by Step
$(7h-2)(7h+2)=$
...identify which terms correspond to $a $ and $b $
...in the rule for the product of a sum and difference ($(a+b)(a-b)=a^{2}-b^{2}$).
$a=7h,\ b=2$
...substitute for $a $and $b $in the rule
$(7h-2)(7h+2)=(7h)^{2}-2^{2}$
...simplify.
=$49h^{2}-4$
