How far apart are P(-3, 5) and Q(2, 7)? Leave your answer in surd form.

$PQ=\sqrt{(2-(-3){)}^2+(7-5{)}^2}=\sqrt{5^2+2^2}=\sqrt{25+4}=\sqrt{29}$, which does not simplify because 29 is prime. The answer 29 forgets the square root, $\sqrt{21}$ comes from subtracting the squares (25 - 4) instead of adding them, and 7 comes from adding the two differences, 5 + 2.