Question

In a certain A.P. the 32nd term is twice the 12th term. Prove that 70th term is twice the 31st term.​

Answer 1

Answer:

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Answer 2

Answer:

Step-by-step explanation:

Solution :-

Let the 1st term be a and the common difference be d.

According to the Question,

a₃₂ = 2a₁₂

a + 31d = 2 (a + 11d)

a + 31d = 2a + 22d

a = 9d         ...(i)

a₇₀ = a + 69d

a₇₀ = 9a + 69d = 78d      [ Putting Eq (i) value]

a₃₁ = a + 30d

a₃₁ = 9d + 30d = 39d      [ Putting Eq (i) value]

a₇₀ = 2a₃₁

Hence Proved.