sum of the first seven terms of an AP is 63 and sum of the next 7 terms is 161.Find the 28th term
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Answer:324,
It was very easy
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Step-by-step explanation:
sum of first n terms=n/2[2a+(n-1)d]
sum of first 7 terms=7/2[2(a)+6d]=63
7[a+3d]=63
a+3d=9----------(1) sum of 1st 14 terms=7[2a+13d]=161+63
2a+13d=32---------(2)
solving (1) and (2)
2a+6d-2a-13d=18-32
7d=14
d=2
a+3(2)=9
a=3
28th term=a+27d
=3+27(2)=3+54=57
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