SOLUTION: the sum of second term and 3rd terms of geometric sequences is 280 and sum of fifth and sixth term is 4375 determine common ratio and 1st term
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Question 1111732: the sum of second term and 3rd terms of geometric sequences is 280 and sum of fifth and sixth term is 4375 determine common ratio and 1st term Answer by ikleyn(52788) (Show Source):
+ = + = = 280. (1)
+ = + = = 4375. (2)
Now divide eq(2) by eq(1) (both sides). After canceling common multipliers, you will get
= = 15.625.
Hence, r = = 2.5.
Thus the common difference is r = 2.5.
The equation (1) the becomes
= 280, which implies = = 32.
Answer. The first term is 32. The common difference is 2.5.
