205

b)
$\overline{OB}=\overline{OA}+\overline{AB}=-3\overline{\text{i}}+7\overline{\text{j}}+8\overline{\text{i}}-2\overline{\text{j}}=5\overline{\text{i}}+5\overline{\text{j}}$
$B=\left(5{,}\ 5\right)$
c)

$\left|\overline{OB}\right|=\sqrt{5^2+5^2}=7{,}07107...cm\approx7cm$