Answer
a. $7225$
b. Yes, for example: $(90-5)^{2}$
Work Step by Step
a. $85^{2}=$
...write $85^{2}$ as the square of a binomial.
$=(80+5)^{2}$
...square the binomial.
$=80^{2}+2(80)(5)+5^{2}$
...simplify.
$=6400+800+25$
...simplify.
$=7225$
b. Yes, for example,
90 is a round number, so we can do the job by
$(90-5)^{2}=8100-2\cdot 5\cdot 90+25$
$=8100-900+25$
$=7225$
