X^2-16x+15 Find the factors of 15... 1x15 -1x-15 3x5 -3x-5 Then add each factor together separately... Which ever one gives you the middle term is the answer... 1+15=16 -1+-15=-16 3+5=8 -3+-5=-8 =1+-15 is the answer so you would put it together like this... (x-1)(x-15)