Question

in the arithmetic progression if an=4n-n*2..then find S1​

Answer 1

$a_{n} = 4n - {n}^{2} \\ a_{1} = 4(1) - {1}^{2} \\ a_1 = 4 - 1 = 3 \\ \\ now, \\ S_{1} = a_{1} = 3$