二次根式运算是初二代数中重点、难点之一,初学者往往由于对混合运算法则及二次根式的性质理解不透、记忆不牢,在运算中易出现各种错误,现举例如下.例1计算18÷34×43.错解原式=18÷1=18.辨析乘法运算满足结合律,而乘除法混合运算时不满足结合律.正解原式=18×43×43=18×43×4 The secondary root-based operation is one of the key and difficult points in the first two algebras. Beginners often do not understand and remember the nature of the mixed algorithm and the secondary roots, and are prone to errors in calculations. The examples are as follows. Example 1 Calculation 18÷34×43. False Solution The original equation = 18÷1=18. The multiplication and multiplication operation satisfies the associative law, and the multiplicative and mixed operation does not satisfy the associative law. The positive solution is equal to 18×43×43=18×. 43×4