Question

the fourth term of an A.P. is 0 prove that it's 25th term is three times the 11th term.

Answer 1

Heya!!

Here is your answer:

a4= 0
a+3d= 0
a= -3d

a25 = a+24d = -3d+ 24d = 21d...............(1)
a11 = a+10 d = -3d+10d = 7d..................(2)

According to question:

a25 = 3(a11)

By equation 1 &2

[21d= 3(7d)]

So, a25 = 3(a11)