Question

The 4th term of an is zero prove that 25 th term of ap is three times its 11th term

Answer 1

a+3d=0
a=-3d

To prove
a25=3(a11)
a+24d=3(a+10d)
a=-3d
-3d+24d=3(-3d+10d)
21d=3(7d)
21d=21d
Hence prove