Question

3+9+7+............30 plzz answer mi​

Answer 1

Answer:

a=3

d=9-3=6

an=2a+(n-1)d

30=2*3+(n-1)6

30=6+6n-6

30=6n

30/6=n

5=n

n=5

sn=n/2(2a+(n-1)d)

=5/2(2*3+(6-1)6)

=5/2(6+30)

=5/2(36)

=5*18

=90