Question

In an A.P. 8, 11, 14 find
Sn-Sn-1​

Answer 1

Answer:

-1

Explanation:

i hope you understand

Answer 2

Answer

Explanation:

a=8

d=a2-a1  

=11-8 = 3

sn=n/2 {2a+[n-1]d}

Sn=n/2(2×8+(n-1)3)

=>Sn=n/2(13+3n)

then,

Sn-1=n-1/2(16+(n-2)3)

=>Sn-1=n-1/2(10+3n)