Question

The sum of first teams of an arithematic sequence is 3n² +4n What is its first team ?
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Answer 1

Answer:

t

n

=s

n

−s

n−1

Tn = 3n^2 + 4n - [ 3( n - 1)^2 + 4( n - 1 )]

3n^2 + 4n - [ 3 ( n^2 + 1 - 2n ) + 4n - 4 ]

3n^2 + 4n - [ 3n^2 + 3 - 6n + 4n - 4 ]

3n^2 + 4n - 3n^2 - 3 + 6n - 4n + 4

6n + 1

Therefore,

algebraic form of an Ap = 6n + 1

More information,

Formula of n terms of an Ap

\bold{a_{n} \: = a \: + (n - 1)d}a

n

=a+(n−1)d

sum of n terms of an Ap

\bold{s_{n} \: = \frac{n}{2} (2a + (n - 1)d)}