2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/133070The problem of simplicity of Fermat number-twins $f_{n}^{\pm}=2^{2^n}\pm3$ is studied. The question for what $n$ numbers $f_{n}^{\pm}$ are composite is investigated. The factor-identities for numbers of a kind $x^2 \pm k $ are found.6 pagesGeneral Mathematics11A51text