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设a为实数,|a|与a哪个大呢?初学者往往认为|a|>a.这是不对的.首先应了解什么叫做一个实数的绝对值.规定如下:一个正数的绝对值是它本身;一个负数的绝对值是它的相反数;零的绝对值是零.即|a|={a(a≥0)-a(a<0)如|3|=3,|0|=0,|-5|=5.所以,当a≥0时,|a|=a,只有当a<0时,才有|a|>a.我们还应了解,|a|的几何意义是指数轴上表示数a的点与原点的距离.
Let a be a real number, | a | and a which is a big deal? Beginners often think that | a |> a. This is not true. First of all should know what is called a real number of absolute value. The following rules: a positive number is It is itself; the absolute value of a negative number is its opposite number; the absolute value of zero is zero. That is, a | = {a (a≥0) -a (a <0) = 0, | -5 | = 5. Therefore, when a≥0, | a | = a, | a |> a is only true if a <0. We should also understand the geometric meaning of | a | Is the distance between the point representing the number a and the origin on the axis.