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

- Oct 1st 2009, 05:50 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

- Oct 1st 2009, 06:58 AMbram kierkels
- Oct 1st 2009, 12:58 PMKrizalid
that's wrong proof.

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