For any prime $p$ not a divisor of $ab$, prove that $ax^2 + by^2 \equiv с \pmod{p}$ is solvable.

Question

Given any integers $a,b,c$ and any prime $p$ not a divisor of $ab$, prove that $ax^2 + by^2 \equiv с \pmod{p} $ is solvable.
$p$ does not divide $ab$ implies $p$ does not divide both $a$ and $b$. But from here how can I show that the aforesaid equation is solvable?