Question 9
Determine how many ordered pairs of integer numbers $(a,b)$ satisfy the following conditions:
- $1\le a,b\le100$ and $a\ne b$.
- $a$ is even.
- $(a-1)\mid(b-1)$, $a\mid b$ and $(a+1)\mid(b+1)$.
- $1\le a,b\le100$ and $a\ne b$.
- $a$ is even.
- $(a-1)\mid(b-1)$, $a\mid b$ and $(a+1)\mid(b+1)$.