How to factorize 8n square + 2s -15

When george started his current job, his employer told him that at the end of the first year, he would receive two vacation days. after each year worked, his number of vacation days will double up to five work weeks (25days) of payed vacation. how many vacation days will he have in 4 years

Pls the last one and it has to be like number 6

Intro biblioteca sunt 462 de carti cu 198 mai putine enciclipedii si cu 47 mai multe dictionare decat enciclopedii cate enciclopedii sunt in biblioteca