Question

प्र.-20 A.P: 21,18, 15-
का कौन सा पद –81 है​

Answer 1

Answer:

n=19

Step-by-step explanation:

21,18, 15,..........

यहाँ a = 21,

d = 18-21 = -3

An = -81 तो n =?

हम जानते हैं कि

An= n + (n-1) * d

-81 = 21 + (n-1) * (- 3)

-81 = 21-3n + 3

3n = 81-24 = 57

3n = 57/3

n = 19