Question

If sn denotes the sum of first n terms of an A.p,then S2- S1=

Answer 1

Answer:

S(n)-S(n-1) is a formula which helps to find the ap

Answer 2

Answer:

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

Put the value of n as 2 for the first time and 1 for the second time and then subtract the values.

S2 = 2/2 ( a + (2-1)d )

S2= a+d

S1=1/2 (a+ (1-1) d )

S1= a/2

S2 -S1

= a+d -a/2

= a/2+d or (a+2d)/2

Hope this helps