Question

the fourth term of an ap is zero prove that 25th term of AP is 3 times its 11 term

Answer 1

a4 = 0
a + 3d = 0
To prove: a25 = 3 a11
a25 = a + 24d = (a+3d)+21d = 21d
a11 = a + 10d = (a+3d)+7d = 7d
Therefore, 21d = 3(7d)
Hence proved.