math500.com

Factorise x² - 8x + 15	Reason:
= (x - 5)(x - 3) factors	Factorise means to write the expression using factors. Each factor is put in a bracket. (x - 5) and (x - 3) are chosen because -5 and -3 add to -8 (the x coefficient) and they multiply to give +15 (the constant).