If $a + b = 4$ and $ab = 3$, find $a^{3} + b^{3}$.

If $a + b = 4$ and $ab = 3$, find $a^{3} + b^{3}$.
  1. $28$
  2. $64$
  3. $36$
  4. $12$

Solution

$(a+b)^{3} = a^{3}+b^{3}+3ab(a+b) \Rightarrow 64 = a^{3}+b^{3}+36 \Rightarrow 28$.

Asked in: IMO

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