So basically I have a mechanics A level tomorrow. And its all great except for one question i've been practising. Was wondering if any of you guys could help. So i get as far as this: t(3t^4 - 4t^2 + 15) And according to the mark scheme i'm supposed to get t[(3t^2 - 5)(t^2 -3)] But i have no idea how to get there? It's obviously some form of factorising or completing a square but im just stuck.. Help would be greatly appreciated :)