Question

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

Answer 1

Answer:

Step-by-step explanation:

Given a4 = 0 That is (a + 3d) = 0 ⇒ a = - 3d → (1) nth term of AP is given by an = a + (n – 1)d a11 = a + 10d = – 3d + 10d = 7d [From (1)] a25 = a+ 24d = – 3d + 24d = 21d [From (1)] = 3 x 7d Hence a25 = 3 x a11

Answer 2

Here is ur answer.........

Let a be the first term and d be the common difference.

Given, a4 = 0

==> a + 3d = 0

==> a = -3d

Now, a25 = a + 24d

==> a25 = 24d - 3d = 21d

and, a11 = a + 10d

==> a11 = 10d - 3d

==> a11 = 7d

But 21d = 3(7d)

==> a25 = 3(a11)


Hope it helps!!