Equations in free groups are not finitely approximable

Equations in free groups are not finitely approximable
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by Thierry Coulbois and Anatole Khelif PDF

Proc. Amer. Math. Soc. 127 (1999), 963-965 Request permission

We give an equation in any free group $F$ of rank $\geq 2$ that has a solution in any finite quotient of $F$, but has no solution in $F$.

References

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