Question

In A.P what is the sn -sn-1 equal to

Answer 1

Answer:

$a + (n - 1)d$

Step-by-step explanation:

$we \: \: know \: \: that \\ \boxed{s_{n} = \frac{n}{2} \ \: [{2a + (n - 1)d \: }\:] } \\ now \\ s_{n} - s_{n - 1} \\ = \frac{n}{2} \ \: [{2a + (n - 1)d \: }\: ] - [\frac{n - 1}{2} \ \: [{2a + (n - 1 - 1)d \: }\: ]] \\ = a + ( n- 1)d$