Chuang和Lee通过在半素环中构造一个可数子环的方法证明如下结果：设R是一个半素环,d为R上的一个导子,假设对于任意x∈R,存在一个依赖于x的多项式gx（t）∈Z（t）,使得d（x-x2gx（x））=0.那么d（R）[R,R]=0.本短文指出：此定理完全可以通过常规的方法来证明.从而说明上面的定理作为Chuang和Lee方法的应用例子是不适合的.%By the method of constructing a countable subring in semiprime rings Chuang and Lee proved the following result ： Let R be a semiprime ring with d a derivation of R. Suppose that for each x R, there is a polynomial gx （t） Z [ t ], depending on x such that d （ x - X2gx （x） ） = 0. Then d （R） [ R, R ] = 0. In this short note we show that this theorem can be proved completely by a routine method. It implies that the above theorem as an application of Chuang and Lee method is not suitable.
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