The age of a father is $(x^{2}-1)$ years and the age of his son is $(x-1)$ years. The ratio of their ages is

The age of a father is $(x^{2}-1)$ years and the age of his son is $(x-1)$ years. The ratio of their ages is
  1. $(x + 1) : 1$
  2. $x : 1$
  3. $(x - 1) : 1$
  4. $(x^{2}+1):(x+1)$

Solution

$\dfrac{x^{2}-1}{x-1} = \dfrac{(x-1)(x+1)}{x-1} = x+1$. So ratio is $(x+1):1$.

Asked in: IMO

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