How many terms of On AP 16.14, 12
are needed to give the sum 60?
Explain why we get double answer?
Answers
Answered by
6
Answer:
12th and 5th term
Step-by-step explanation:
Sn = n/2[2a+(n-1)d]
60 = n/2[2×16+(n-1)(-2)]
60=n/2[32-2n+2]
60=n/2[-2n+34]
60=n/2[2(-n+17)]
60=n(-n+17)
n(17-n) = 60
-n²+17n-60=0
n²-17n+60=0
n²-12n-5n+60=0
n(n-12)-5(n-12)=0
(n-12)(n-5)=0
n= 12 or 5
Here, We are getting to different answers because the common difference of A.P. is in negative.
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