x3−13x2+32x+20
=x3+13x2+30x+2x+20
=x(x2+13x+30)+2x+20 [Taking x as common]
=x(x2+10x+3x––––––––––+30)+2(x+10)
=x{x(x+10)+3(x+10)}+2(x+10)
=x(x+3)(x+10)+2(x+10)
=(x+10){x(x+3)+2}
=(x+10)(x2+3x+2)
=(x+10)(x2+2x+x+2)
=(x+10){x(x+2)+1(x+2)}
=(x+10){(x+1)(x+2)}
=(x+10)(x+1)(x+2)