If the sum of the first n terms of an A.P. is 4n−n², what is the first term (that is S₁)?

If Sum of first n terms of an A.P. Sn = 4n−n²
Then, the first term will be when n=1 in the above expression
S₁ = a = 4(1)−(1)² = 3
Sum of first two terms, n=2, S₂ = 4(2)−2² = 4
So, the second term will be a₂ = S₂−S₁ = 4−3 = 1
Similarly
n=3, S₃ = 4(3)−3² = 3 ⇒ a₃ = S₃−S₂ = 3−4 = −1;
n=9, S₉ = 4(9)−9² = −45
n=10, s₁₀ = 4(10)−(10)² = −60 ⇒ a₁₀ = S₁₀−S₉ = −60−(−45) = −15
an = Sn−S(n−1) ⇒ an = 4n−n²−(4(n−1)−(n−1)²) ⇒ an = 5−2n