Question

Which term of the A.P. - 21 ,18 15 ...is -81 .Also is any term 0. Give reason for your answer .​

Answer 1

The given Arithmetic Progression is 21, 18, 15,…,0,….

The first term = a = 21

Now the common difference = d = -3

nth term = 0

We need to find n.

nth term = a + (n-1)d

0 = 21 + (n-1)(-3)

⇒ 3(n-1) = 21

⇒ n-1 = 7

⇒ n = 8

⇒ The 8th of the given Arithmetic Progression is 0.

Answer 2

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Step-by-step explanation:

The given Arithmetic Progression is 21, 18, 15,…,0,….

The first term = a = 21

Now the common difference = d = -3

nth term = 0

We need to find n.

nth term = a + (n-1)d

0 = 21 + (n-1)(-3)

⇒ 3(n-1) = 21

⇒ n-1 = 7

⇒ n = 8

⇒ The 8th of the given Arithmetic Progression is 0.

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