Question

given a=7,a1 =35,find 'd' and S13​

Answer 1

Step-by-step explanation:

a = 7

a1 = 35

d = a1 - a

d = 35 - 7

d = 28

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

S13 = 13/2 (2×7+(13-1)28)

S13 = 13/2(14+(12)28 )

S13 = 13/2(14+336)

S13 = 13/2(350)

S13 = 2275