If the sum of the first n terms of an AP is 4n-n2,what is the first term (that is S1)?

We can find the first term as follows:

S₁ = 4 × 1 - 1² = 3

Now; sum of first two terms can be calculated as follows:

S₂ = 4 × 2 - 2²

= 8 - 4 = 4

Hence; second term = 4 – 3 = 1

And d = 1 – 3 = - 2

So, 3rd term can be calculated as follows:

a₃ = a + (n – 1)d

= 3 + 2( - 2) = 3 – 4 = - 1

Similarly, 10th term can be calculated as follows:

a₁₀ = a + 9d

= 3 + 9(- 2)

= 3 – 18

= - 15