Answer
$(y+4)(y-5)(2y-1)$
Work Step by Step
$y^2-y-20=y^2-5y+4y-20=y(y-5)+4(y-5)=(y-5)(y+4)$, $2y^2+7y-4=2y^2+8y-y-4=2y(y+4)-(y+4)=(y+4)(2y-1)$, so the GCF is $(y+4)$ and the terms that are "not common" are $(y-5),(2y-1)$ so LCD$=(y+4)(y-5)(2y-1)$
