隐含条件往往不易发现和容易忽视 ,当同学们在求有关a型问题时 ,自然会想到a中a≥ 0这一条件 ,但当a被其它条件掩盖时 ,常常会忽略a≥ 0这一隐含条件。例 1　若关于x的方程x2 - 2kx - 1 =0有两个不相等的实数根 ,求k的取值范围 ?错解 :∵方程有两个不相等的实数根∴△ =(- 2k) Implicit conditions are often difficult to find and easy to ignore. When students are asking questions about type a, they naturally think of the condition that a≥0 in a, but when a is covered by other conditions, it often ignores a≥0. Implicit conditions. Example 1 If the equation x2 - 2kx - 1 =0 about x has two unequal real roots, find the range of k: the wrong solution: The ∵ equation has two unequal real numbers ∴ △ = (- 2k)