## Algebra 1: Common Core (15th Edition)

a. $7225$ b. Yes, for example: $(90-5)^{2}$
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 $(90-5)^{2}=8100-2\cdot 5\cdot 90+25$ $=8100-900+25$ $=7225$