Question

What is the 5th term of an arithmetic sequence if t3 = 10 and t7 = 26

Answer 1

t 1 + 2 d = 10 / * ( - 1 )
t 1 + 6 d = 26
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- t 1 - 2 d = - 10
+
  t 1 + 6 d = 26
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         4 d = 16,  d = 4
  t 1 + 8 = 10
  t 1 = 2
  t 5 = t 1 + 4 d = 2 + 4 * 4 = 2 + 16 = 18
 Answer: the 5th term of this sequence is 18.