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CBSE Class 10 Answered

In an A.P sum of the first 2 term is 5 and sum of the last 2 term is 129. Then find the sequence 
Asked by dhruthanmn | 06 Jun, 2020, 03:35: PM
Expert Answer
According to the question,
a + (a+d) = 5
2a + d = 5 .... (i)
a+(n-2)d+a+(n-1)d=129
2a + d(2n-3) = 129 ... (ii)
Subtracting (i) from (ii), we get
d(2n-4) = 124
d(n-2) = 62
n = 62/d + 2
Since n has to be a non-zero positive integer.
Therefore, d can take the values 1, 2, 31 or 62
Basis on this, find the value of a and hence the sequence.
Answered by Renu Varma | 06 Jun, 2020, 09:07: PM

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