0,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">
2 -4 8
-16 （32） 构成公比为-2的等比数列
因此A项当选。
57．【解析】C。二次作差。2=![]()
600)makesmallpic(this,600,1800);\' width=\"25\" height=\"23\" style=\"vertical-align: middle;\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718893058.png\">，3=![]()
600)makesmallpic(this,600,1800);\' width=\"24\" height=\"24\" style=\"vertical-align: middle;\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718731059.png\">，![]()
600)makesmallpic(this,600,1800);\' width=\"33\" height=\"24\" style=\"vertical-align: middle;\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193717367003.png\">=![]()
600)makesmallpic(this,600,1800);\' width=\"33\" height=\"24\" style=\"vertical-align: middle;\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718045060.png\">。只看底数：
2 4 9
17 28 （42） 后项减前项
![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">
2 5 8
11 （14） 再次作差
![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">
3 3 3
3
因此括号中的数是![]()
600)makesmallpic(this,600,1800);\' width=\"33\" height=\"23\" style=\"vertical-align: middle;\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193717442004.png\">，C项当选。
58．【解析】A。整数部分作差1，3，9，27，（81），44+81=125。小数部分4=2×2，5=2×2+1，8=4×2，17=8×2+1，44=22×2，125=62×2+1，答案为125.62，因此A项当选。
59．【解析】B。三次作差。
7 14 33
70 131 （222） 后项减前项
![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">
7 19 37
61 （91） 再次作差
![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">
12 18 24
（30） 再次作差
![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/uploadfile/2017/03/01/20170301193718909057.png\">![]()
600)makesmallpic(this,600,1800);\' width=\"49\" height=\"12\" border=\"0\" src=\"/ewebeditor/up
