the sum of first n terms of an AP is given by a Sn is equal to 2n^2+ 3n. Find the sixteenth term of the AP.
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I'll take the first element as A1 instead of A0, and so on..
Sum of AP is given by
Sn=n(A1+An)/2
or
2n^2+3n = n(A1+An)/2
or
4n+6= A1+An or
4n+6 = 2A1+ (n-1)d
Let n=16,
So
70=2A1+15d
or A16+A1=70
A16=70-A1
S1=A1
And S1=5
So A16=65
Sum of AP is given by
Sn=n(A1+An)/2
or
2n^2+3n = n(A1+An)/2
or
4n+6= A1+An or
4n+6 = 2A1+ (n-1)d
Let n=16,
So
70=2A1+15d
or A16+A1=70
A16=70-A1
S1=A1
And S1=5
So A16=65
vishal348:
Is it correct?
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