原式=3.99×0.39×1-3.99×0.39×0.01=（4×0.39-0.01×0.39）-（4×0.39×0.01-0.01×0.39×0.01)=4×0.39-0.01×0.39-0.04×0.39+0.000039=1.56-0.05×0.39+0.000039=1.540539简单地说,原式=（4-0.01）×（1-0.01...