We construct parametric families of (monic) reducible polynomials having two roots very close to each other.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-aa162-4-6,
author = {Yann Bugeaud and Andrej Dujella},
title = {Root separation for reducible integer polynomials},
journal = {Acta Arithmetica},
volume = {166},
year = {2014},
pages = {393-403},
zbl = {1290.11056},
language = {en},
url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-aa162-4-6}
}
Yann Bugeaud; Andrej Dujella. Root separation for reducible integer polynomials. Acta Arithmetica, Tome 166 (2014) pp. 393-403. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-aa162-4-6/