if sn the sum of first n terms is given by sn= 5n2+3n find its n th tern
Answers
Answered by
3
Putting n=1
S1=5×1^2 +3×1
S1=8
First term=8
Putting n=2
S2=5×2 ^2 +3×2
S2=26
SECOND TERM =26-8
=18
SERIES WILL BE 8 18 28 38
A=8
D=18
An=a+(n-1 ) d
=8+(n-1 )10
8+10n-10
10n-2
Answer
S1=5×1^2 +3×1
S1=8
First term=8
Putting n=2
S2=5×2 ^2 +3×2
S2=26
SECOND TERM =26-8
=18
SERIES WILL BE 8 18 28 38
A=8
D=18
An=a+(n-1 ) d
=8+(n-1 )10
8+10n-10
10n-2
Answer
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Answered by
1
We know that
An=Sn-Sn-1
An=5n2+3n-[5(n-1)2+3(n-1)]
An=5n2+3n-[5(n2-2n+1)+3n-3]
An=5n2+3n-5n2+10n-5+3n-3
An=6n+10n-8
An=16n-8
An=Sn-Sn-1
An=5n2+3n-[5(n-1)2+3(n-1)]
An=5n2+3n-[5(n2-2n+1)+3n-3]
An=5n2+3n-5n2+10n-5+3n-3
An=6n+10n-8
An=16n-8
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