一般地,我们把形如a~(1/2)(a≥0)的式子叫做二次根式.由于在实数范围内,负数没有平方根,所以被开方数a只能是非负数,即a≥0.又因为a~(1/2)表示非负数a的算术平方根,也只能是非负数,即a~(1/2)≥0.深入理解二次根式的非负性是学习二次根式的关键,同时也是解题中要特别注意挖掘的隐含条件.现举例说明在解题中如何利用这一隐含条件,希望对同学们能有所帮助. In general, we call a radical of the form a ~ (1/2) (a ≥ 0) as a quadratic radical. Since there is no square root in the real number range, the square root of the square a can only be a non- ≥0. And because a ~ (1/2) means that the non-negative arithmetic a square root of a, it can only be non-negative, that is, a ~ (1/2) ≥ 0. In-depth understanding of the quadratic root- At the same time, it is also an implied condition that special attention should be paid to excavation.Here we give an example to illustrate how to use this implied condition in the problem solving and hope that it can be helpful to the students.