①y=x2-5x-14=(x-7)(x+2)=0, 得：x=7, -2②y=-x2-x+20=-(x^2+x-20)=-(x+5)(x-4)=0, 得：x=-5, 4③y=（x-1)(x2-3x+1), 得：x=1, (3+√5)/2, (3-√5)/2④f(x)=(x2-2）（x2-3x+2)=(x^2-2)(x-1)(x-2)=0, 得:x=√2, -√2, 1, 2
