1.计算:(1)3(2).ab23(2)1.5(2).xx2231(3)()().22stst32(4)(2)2.aab解:(1)3(2)6.abab235(2)1.5(2)3.xxx2233313(3)()().224ststst3242(4)(2)216.aabab2.1cm3干洁空气中大约有2.5×1019个分子,6×103cm3干洁空气中大约有多少个分子?6×103×2.5×1019=1.5×1023.答:6×103cm3干洁空气中大约有1.5×1023个分子.3.计算:(1)2().abc(2)(3)(6).xyx224(3)3(5).9aaa2251(4)4(3).124xyxxyy解:(1)2()222.abcabc2(2)(3)(6)618.xyxxxy22344(3)3(5)154.93aaaaa223223515(4)4(3)12.1243xyxxyyxyxyxy