Question

Find S25 for 3 + 7 + 11 + 15 + …

Answer 1

1]
d = 7 - 3 = 4
a = 3
Sn = n/2 [2a + (n-1)d]
S25 = 25/2 [2*3 + (25-1)4]
= 25/2 [6 + 96] = 25 * (3 + 48) = 25 * 51 = 1275

2] d = 1/2 - 0 = 1/2

3]
There are 4 terms between 40 and 10.
d = (10 - 40) / (4+1) = -30/5 = -6
a = 40
AP is 40, 34, 28, 22, 16, 10

4]
d = 0 - (-3) = 3
next terms are 9 + 3 = 12, 12 + 3 = 15
next 2 terms = 12, 15

Answer 2

If u didnt understand: https://answers.yahoo.com/question/index?qid=20110117220735AAZHyhk

Answer 3

@sheesh28