思路二:2×15-2=28,2×28-2=54, 2×54-2=106,2×106-2=210,
【218】 2,4,8,24,88,( )
A.344;B.332; C.166;D.164;
分析:答案A,每一項(xiàng)減第一項(xiàng)=>2,4,16,64,256=>第二項(xiàng)=第一項(xiàng)的2次方,第三項(xiàng)=第一項(xiàng)的4次方,第四項(xiàng)=第一項(xiàng)的6次方,第五項(xiàng)=第一項(xiàng)的8次方,其中2,4,6,8等差
【219】22,35,56,90,( ),234
A.162;B.156;C.148;D.145;
分析:答案D,后項(xiàng)減前項(xiàng)=>13,21,34,55,89,第一項(xiàng)+第二項(xiàng)=第三項(xiàng)
【220】1,7,8, 57, ( )
A.123;B.122;C.121;D.120;
分析:答案C,12+7=8,72+8=57,82+57=121
【221】1,4,3,12,12,48,25,( )
A.50;B.75;C.100;D.125
分析:答案C,第二項(xiàng)除以第一項(xiàng)的商均為4,所以,選C100
【222】5,6,19,17,( ),-55
A.15;B.344;C.343;D.11;
分析:答案B,5的平方-6=19,6的平方-19=17,19的平方-17=344,17平方-344=-55
【223】3.02,4.03,3.05,9.08,( )
A.12.11;B.13.12;C.14.13;D.14.14;
分析:答案B,小數(shù)點(diǎn)右邊=>2,3,5,8,12 二級(jí)等差,小數(shù)點(diǎn)左邊=>3,4,3,9,13 兩兩相加=>7,7,12,22 二級(jí)等差
【224】95,88,71,61,50,( )
A.40;B.39;C.38;D.37;
分析:答案A,95 - 9 - 5 = 81,88 - 8 - 8 = 72,71 - 7 - 1 = 63,61 - 6 - 1 = 54,50 - 5 - 0 = 45,40 - 4 - 0 = 36 ,其中81,72,63,54,45,36等差
【225】4/9,1,4/3,( ),12,36
A.2;B.3;C.4;D.5;
分析:答案C,4/9,1, 4/3,( )12,36=>4/9,9/9,12/9,36/9,108/9,324/9,分子:4,9,12,36,108,324=>第一項(xiàng)×第二項(xiàng)的n次方=第三項(xiàng), 4×(9(1/2))=12,4×(91)=36,4×(9(3/2))=108,4×(92)=324,其中1/2,1,3/2,2等差,分母:9,9,9,9,9,9等差
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