Question

If the nth term of a sequence is 5+2n,then the sum of first 20 terms and 30 terms are​

Answer 1

Answer:S20=520

S30=1080

Step-by-step explanation:

Tn=5+2n

T1=a=5+2 (1)=5+2=7

T2=5+2 (2)=5+4=9

Common difference =T2-T1=9-7=2

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

S20=20/2 (2 (7)+(20-1)2) = 10 (14+19 (2)) =10 (14+38) = 10 (52) =520//

S30=30/2 (2 (7)+(30-1)2) = 15 (14+29 (2)) = 15 (14+58) = 15 (72) = 1080//