方法一:相减法
(x-3)²=x²-6x+9
(x-2)(x-4)=x²-6x+8
两式相减
(x-3)²-(x-2)(x-4)
=(x²-6x+9)-(x²-6x+8)
=(x²-x²)+(6x-6x)+(9-8)
=1>0
即(x-3)²>(x-2)(x-4)
方法二:直接比较法
(x-2)(x-4)
=[(x-3)+1][(x-3)-1] (x-2)(x-4)
方法一:相减法
(x-3)²=x²-6x+9
(x-2)(x-4)=x²-6x+8
两式相减
(x-3)²-(x-2)(x-4)
=(x²-6x+9)-(x²-6x+8)
=(x²-x²)+(6x-6x)+(9-8)
=1>0
即(x-3)²>(x-2)(x-4)
方法二:直接比较法
(x-2)(x-4)
=[(x-3)+1][(x-3)-1] (x-2)(x-4)