\((-2-\dfrac{1}{3}i)^3\)
\(=-[2^3+(\dfrac{i}{3})^3+3.(2)(\dfrac{i}{3})(2)(2+\dfrac{i}{3})]\)
\(=-[8+\dfrac{i^3}{27}+2i(2+\dfrac{i}{3})]\)
\(=-[8-\dfrac{i}{27}+4i-\dfrac{2}{3}]\)
\(=-[\dfrac{22}{7}+\dfrac{107}{27}i]\)
\(=-\dfrac{22}{3}-\dfrac{107}{27}i\) (Ans.)