If \\alpha , \\beta are the roots of a x ^ { 2 } + b x + c = 0 then { \\alpha ^ { 3 } + \\beta ^ { 3 } }/ { \\alpha^ { - 3 } + \\beta^ { - 3 } } =

{ 3 a b c - b ^ { 3 } }/ { c ^ { 3 } }