Question

find sum of 8 terms of an AP is 100 and sum of first 19 terms is 551​

Answer 1

Step-by-step explanation:

Let a be first term and d be common difference

A/q

(8/2)[2a+(8-1)d] = 100

⇒2a + 7d =25_____(1)

and (19/2)[2a + (19-1)d] = 551

⇒2a + 18d = 58____(2)

subtracting equation (1) and (2)

11d = 33

⇒d = 3

so a = (25 - 21)/2 = 2

so AP = 2,5,8.11,14.......