\(\dfrac{423134\cdot846267-423133}{846267\cdot423133+423134}\)
\(=\dfrac{(423133+1)\cdot846267-423133}{846267\cdot423133+423134}\)
\(=\dfrac{423133\cdot846267+846267-423133}{846267\cdot423133+423134}\)
\(=\dfrac{423133\cdot846267+423134}{864267\cdot423133+423134}=1\)