Question

The sum of n terms of an AP is 3n2 + 4n . Find the AP​

Answer 1

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Step-by-step explanation:

T

n

=S

n

−S

n−1

.(1)

Now S

n

=3n

2

+4n

∴S

n−1

=3(n−1)

2

+4(n−1)=3n

2

−2n−1

∴T

n

=(3n

2

−4n)−(3n

2

−2n−1), by (1)

=6n+1

∴T

1

=7,T

2

=13,T

3

=19,______

∴a=7,d=6.