Answers

2016-07-27T16:40:54+08:00
Harmonic sequence: -2/3, -4/7, -1/2, -4/9 ....
the reciprocals are the terms of an arithmetic sequence
    -3/2, -7/4, -2/1, -9/4 or rewriting it with 4 as the denominator
    -6/4, -7/4, -8/4, -9/4, ... thus the 15 term is a15 = a1 + (15-1)d
                                                                              = -6/4 + 14(-1/4)
                                                                              = -3/2 - 7/2
                                                                              = -10/2
                                                                        a15 = -5
 therefore the 15th term of the harmonic sequence is the reciprocal of -5 which is -1/5.
hope it will help.
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