Question 199
a) Factorize $xy - x - y + 1$.
b) Prove that if integers $a$ and $b$ satisfy $|a+b| \gt |1+ab|$, then $ab = 0$.
b) Prove that if integers $a$ and $b$ satisfy $|a+b| \gt |1+ab|$, then $ab = 0$.
MathNet 2010 — Part 04 Question 199
Math Olympiad Vault · MathNet 2010 — Part 04