Sequences and Series (001)
来源:学生作业帮 编辑:作业帮 分类:英语作业 时间:2024/10/06 07:50:49
Sequences and Series (001)
If the first,fifth and tenth terms of an arithmetic progression are in geometric progression and the sum of the second and eighth terms is 20,find the first term and the (non-zero) common difference.
If the first,fifth and tenth terms of an arithmetic progression are in geometric progression and the sum of the second and eighth terms is 20,find the first term and the (non-zero) common difference.
Solution:let the geometric progression a、a+4d and a+9d.
∴q^2=(1+4d/a)^2=1+9d/a.
∴d/a=1/16,or d/a=-1/16.
When d/a=-1/16,it is not to fit this question .
So d/a=1/16.
∴ a=16d.
∵(a+q)+(a+7q)=20
∴a+4d=10
∵20d=10
∴d=1/2
∴ a=8
∴q^2=(1+4d/a)^2=1+9d/a.
∴d/a=1/16,or d/a=-1/16.
When d/a=-1/16,it is not to fit this question .
So d/a=1/16.
∴ a=16d.
∵(a+q)+(a+7q)=20
∴a+4d=10
∵20d=10
∴d=1/2
∴ a=8
Sequences and Series (001)
Sequences and Series (003)
sequences和series的区别
什麽是Arithmetic and Geometric Sequences
c++ACM简单题Description Given two integer sequences A and
AMD Radeon 6600M and 6700 Series
methane- and ethane-series什么意思
请尽快帮我翻译个概述,3100 Series and 3200 Heavy Duty Series Compact OE
JACK AND THE BEANSTALK FLTRP INTERACTIVE STORYBOOK SERIES LI
Sequences in second language acquistion什么意思
on series
a series