Compute $123^{2} - 23^{2}$ using $a^{2}-b^{2}$.

Compute $123^{2} - 23^{2}$ using $a^{2}-b^{2}$.
  1. $14600$
  2. $10000$
  3. $13600$
  4. $12300$

Solution

$123^{2}-23^{2} = (123-23)(123+23) = 100 \times 146 = 14600$.

Asked in: IMO

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