在二次根式的化简与运算中,常常设伏着一些隐含条件,即使二次根式有意义的条件下,字母的取值范围.这类隐含条件,往往使同学感到解题困难.化如果在化简之前,首先考虑到这一点,把它作为题中的已知条件,就会思路清晰,轻松解题,现举例说明. In the simplification and operation of secondary roots, some implicit conditions are often set. Even if the secondary roots are meaningful, the range of the letter’s value, such implicit conditions, often make the students feel that it is difficult to solve problems. If, before simplification, first consider this point, and use it as a known condition in the question, it will be clear and easy to solve the problem.