Question

find the nth to and sum upto n terms of the following series
1.2+3.4+5.6+7.8+...​

Answer 1

Answer:

$0.1n + 1.1 {n}^{2}$

Step-by-step explanation:

a=1.2

d = 2.2

n = n

sum = n/2[2a+(n-1)d]

= n/2[2×1.2+(n-1) 2.2]

=n/2[2.4+2.2n-2.2]

=n/2[0.2+2.2n]

= 0.1n+1.1(n^2)