SOLUTION: Please help me solve this equation. The second and seventh term of a g.p are 18 and 4374 respectively find the (a) common ratio (b) sum of 4th and 8th terms (c) sum of the first 1

Algebra ->  Sequences-and-series -> SOLUTION: Please help me solve this equation. The second and seventh term of a g.p are 18 and 4374 respectively find the (a) common ratio (b) sum of 4th and 8th terms (c) sum of the first 1      Log On


   

Question 998359: Please help me solve this equation. The second and seventh term of a g.p are 18 and 4374 respectively find the (a) common ratio (b) sum of 4th and 8th terms (c) sum of the first 10 terms please help me
Answer by ikleyn(52787) About Me  (Show Source):
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The second and seventh term of a geom. progression are 18 and 4374 respectively find the  (a) common ratio  (b) sum of  4th and 8th terms  (c) sum of the first 10 terms.
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a%5B2%5D = a%5B1%5D.q   =   18     (1)

a%5B7%5D = a%5B1%5D.q%5E6 = 4374     (2)


Divide (2) by (1). You will get


q%5E5 = 4374%2F18 = 243.


Hence, q = root%285%2C+243%29 = 3.


It implies a%5B1%5D = a%5B2%5D%2Fq = 18%2F3 = 6.


Now, when you know a%5B1%5D = 6 and q = 3, you can calculate all remaining values.