Answers

2015-10-06T10:45:09+05:30
Sn=2n^2+5n
S1=a1=2(1)^2+5(1)=2+5=7
s2=2(2)^2+5(2)=8+10=18
a2=s2-s1 =18-7=11
similarly an(nth term)=sn-sn-1
sn=2n^2+5n
Sn-1=2(n-1)^2+5(n-1)
2(n^2-2n+1)+5(n-1)
2n^2-4n+2+5n-5
2n^2+n-3
nth term=2n^2-2n^2-5n-n+3
=4n+3
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