SOLUTION: the 10th term of an AP is -27 and the 5th term is -12. what is the 18th term. find also the sum of its 28th terms
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Question 1053935: the 10th term of an AP is -27 and the 5th term is -12. what is the 18th term. find also the sum of its 28th terms Answer by ikleyn(52775) (Show Source):
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the 10th term of an AP is -27 and the 5th term is -12. what is the 18th term. find also the sum of its 28th terms
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(1) = + 9*d,
(2) = + 4d.
or
(1') -27 = + 9*d,
(2') -12 = + 4d.
Distract (2') from (1'). You will get
-15 = 5d ---> d = -3.
Then from (1') = -27 - 9*(-3) = -27 + 27 = 0.
Answer. = 0, d = -3.
Now you can easily answer your questions.
