Question

The 4th term of an ap is 0.Prove that the 25th termis

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

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

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