We know that,

a³ + b³ + c³ – 3abc = (a + b + c) (a² + b² + c² – ab – bc – ca)]

Using this formula, we get

= (a)³ + (2b)³ + (4c)³ – 3 (a) (2b) (4c)

= (a + 2b + 4c) (a² + 4b² + 16c² – 2ab – 8bc – 4ac)