The sum of first n terms of an AP is 5n square +3n . If it's mth terms is168 . Find the value of m and also find its AP
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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)
=5n^2+3n-5n^2+10n-5-3n+3
=10n-2
hence
tn=10n-2
again question ask
tm=168
168=10m-2
m=170/10=17
Sn=5n^2+3n
we know
tn=Sn-S(n-1)
=5n^2+3n-5 (n-1)^2-3 (n-1)
=5n^2+3n-5n^2+10n-5-3n+3
=10n-2
hence
tn=10n-2
again question ask
tm=168
168=10m-2
m=170/10=17
abhi178:
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