If a, b and c are positive real numbers, prove that 4(a³ + b³) ≥ (a + b)³ & that 9(a³ + b³ + c³) ≥ (a + b + c)³

- October 1st 2009, 04:50 AMMozartIf a, b and c are positive real numbers, prove that 4(a³ + b³) ≥ (a + b)³
If a, b and c are positive real numbers, prove that 4(a³ + b³) ≥ (a + b)³ & that 9(a³ + b³ + c³) ≥ (a + b + c)³

- October 1st 2009, 05:58 AMbram kierkels
- October 1st 2009, 11:58 AMKrizalid
that's wrong proof.

to fix it, in each step you need to add an