the sum of first n term of an ap is 5n2 - 3n find nth term and also 10th term
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given ,
Sn=5n^2-3n
we know,
tn=Sn - S (n-1)
=5n^2-3n-5 (n-1)^2+3 (n-1)
=5 {n^2-n^2+2n-1}-3 {n-n+1}
=10n-8 (answer)
now ,
t10=10 x 10 -8= 92 (answer)
Sn=5n^2-3n
we know,
tn=Sn - S (n-1)
=5n^2-3n-5 (n-1)^2+3 (n-1)
=5 {n^2-n^2+2n-1}-3 {n-n+1}
=10n-8 (answer)
now ,
t10=10 x 10 -8= 92 (answer)
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