Expanding - or geting rid of brackets. Make sure you multiply everything by everything! Correct: p2 +2p -5p -10 = p2 -3p -10 Wrong: p2 + 2p -5 ...forgot that the -5 also needs to be multiplied by (p+2) Wrong: p2 - 10 ...only multiplied the end bits Wrong: p + 2p -5p -10 ... forgot that p x p = p2