一道等比数列数学题
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一道等比数列数学题
![](http://img.wesiedu.com/upload/3/c8/3c8224d4765c76658082158d16372fd9.jpg)
![](http://img.wesiedu.com/upload/3/c8/3c8224d4765c76658082158d16372fd9.jpg)
![一道等比数列数学题](/uploads/image/z/16411519-55-9.jpg?t=%E4%B8%80%E9%81%93%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97%E6%95%B0%E5%AD%A6%E9%A2%98)
a5-a1=a1(q^4-1)=a1(q^2+1)(q^2-1)=15````````````1
a4-a2=a1q(q^2-1)=6```````````````````````````````````2
1、2相比得:得:q^2+1=5q/2 即:q=2 或 q=1/2 (舍去)
q=2则a1=1
a3=a1q^2=4
a4-a2=a1q(q^2-1)=6```````````````````````````````````2
1、2相比得:得:q^2+1=5q/2 即:q=2 或 q=1/2 (舍去)
q=2则a1=1
a3=a1q^2=4