Question
Prove or disprove: If $a$ has an inverse modulo $b,$ then $b$ has an inverse modulo $a$.
Step 1
If $a$ has an inverse modulo $b$, then there exists an integer $x$ such that $ax \equiv 1 \pmod{b}$. In other words, $ax = 1 + kb$ for some integer $k$. Show more…
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