Evaluate $a^3 - \dfrac{1}{a^3}$ if $a - \dfrac{1}{a} = 0$.
\(a^3 - \dfrac{1}{a^3}$ if $a - \dfrac{1}{a} = 0 \)
a^3 - 1/a^3 = ( a - 1/a) ( a^2 + 1 +1/a^2) = (0)(a^2 + 1 + 1/a^2) = 0
