分式的加减运算常需要通分．有些运算的分式较复杂，若不运用通分技巧，一动手就求最简公分母，用一次通分的方法，往往使运算繁杂．反之，整体观察各分式的分子、分母的不同特征，灵活运用解题技巧，则能化繁为简，事半功倍．一、先约分后通分分析本题特征：前两个分式的分子 Fractional additions and subtractions often require pass points. Some operations have more complex divisions. If you do not use the pass-through technique, you will seek the simplest public denominator at a time. Using a pass-through method will often complicate operations. On the contrary, the overall observation of the different characteristics of the fractions of the numerator and denominator, and the flexible use of problem-solving techniques, can be simplified and more effective. First, analyze the characteristics of this question by first analyzing the points after splitting: the first two fractions of the molecule