/ 3\ |1 a | lim |-- - a - --| x->a+| 3 x | \x /
Limit(x^(-3) - a - a^3/x, x, a)
/ 3\ |1 a | lim |-- - a - --| x->a+| 3 x | \x /
/ 4 5\ -\-1 + a + a / ---------------- 3 a
/ 3\ |1 a | lim |-- - a - --| x->a-| 3 x | \x /
/ 4 5\ -\-1 + a + a / ---------------- 3 a
-(-1 + a^4 + a^5)/a^3
/ 4 5\ -\-1 + a + a / ---------------- 3 a