Question

What is the sum of first 40 terms 1+3+4+5+7+7+10+9+........ Brainly?

Answer 1

Sn=n/2 (2a+(n-1) d)
= 40/2 (2+39*2)
20*80
1600

Answer 2

Answer:

Step-by-step explanation:

1+3+4+5+7+7+10+9....

=(1+4+7+10...upto 20 terms)+(3+5+7+9...upto 20 terms)

=(10(2*1+19*3)) + (10(2*3+19*2))

[•Sn=n/2(2a+(n-1)*d)]

=(10*59)+(10*44)

=590+440

=1030.