If a--b = 4 and ab = 45, find the value of a3 - b3

$$\begin{gathered} ( a ? b ) 2 = a 2 + b 2 - 2 ab \\ ? 16 = a 2 + b 2 ? 90 \\ ? a 2 + b 2 = 106 \\ a 3 ? b 3 = ( a ? b ) ( a 2 + b 2 + ab ) \\ ? a 3 ? b 3 = 4 X ( 106 + 45 ) \\ ? a 3 ? b 3 = 4 X 151 \\ ? a 3 ? b 3 = 604 \end{gathered}$$