Question

b. 3+7+13+21+ ...... upto n term
A.P series math..​

Answer 1

Hey!

a = 3

d = 4

an = 3 + (n-1)4

an = 3+ 4n - 4

an = 4n - 1

Sum of n terms

= Sn

Sn = $\frac{n}{2}$ (2(3) + (n-1)4)

Sn = $\frac{n}{2}$ (6+4n-4)

Sn  = $\frac{n}{2}$ (4n - 2)

Sn = n(2n - 1)

Sn = 2n²-n