Question

Find the sum of at 2+5+8., to 20 terms using formulas​

Answer 1

Answer:

In the given A.P.

First trem,a=2

Common difference,d=5-2

=3

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

S20=20/2[2×2+(20-1)3]

=10[4+19×3]

=10(4+57)

=10×61

=610.

Here is your answer.

Answer 2

by using the formula you will get 610 as your answer