SOLUTION: Find the first term & common difference if:
10th term is 35;15th terms is 55
2nd term is 56 ;12th term is 16
8th term is 4;18th term is -96
7th term is -25;2th term is -45
Algebra ->
Sequences-and-series
-> SOLUTION: Find the first term & common difference if:
10th term is 35;15th terms is 55
2nd term is 56 ;12th term is 16
8th term is 4;18th term is -96
7th term is -25;2th term is -45
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Question 1087946: Find the first term & common difference if:
10th term is 35;15th terms is 55
2nd term is 56 ;12th term is 16
8th term is 4;18th term is -96
7th term is -25;2th term is -45 Answer by ikleyn(52794) (Show Source):
1) 10th term is 35; 15th terms is 55
2) 2nd term is 56 ; 12th term is 16
3) 8th term is 4; 18th term is -96
4) 7th term is -25; 2th term is -45
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I will solve #1 only. Do the remaining cases following the same pattern.
1) 10th term is 35; 15th terms is 55.
Between the 10-th and 15-th terms, there is the room for 5 (=15-10) common differences d.
So, 5d = 55 - 35 = 20. Hence, d = = 4.
Thus you just found the common difference d = 4.
Then from = + 9*d you have
= - 9d = 35 - 9*4 = 35 - 36 = -1.
Answer. = -1; d = 4.
