The 7th term of an A.P. is −1 and its 16th term is 17. The nth term of the A.P. is :
(3n + 12)
(2n − 5)
(3n + 5)
(2n − 15)
AP
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Question

The 7th term of an A.P. is −1 and its 16th term is 17. The nth term of the A.P. is : 1. (3n + 12) 2. (2n − 5) 3. (3n + 5) 4. (2n − 15)

KnowledgeBoat · Accepted Answer

We know that, an = a + (n - 1)d The 7th term of an A.P. is −1. a + 6d = -1 ......(1) The 16th term of an A.P. is 17. a + 15d = 17 ......(2) Subtract Equation (1) from Equation (2) : ⇒ a + 15d - (a + 6d) = 17 - (-1) ⇒ a + 15d - a - 6d = 18 ⇒ 9d = 18 ⇒ d = ⇒ d = 2. Substituting d = 2 into Equation (1), we get : ⇒ a + 6(2) = -1 ⇒ a + 12 = -1 ⇒ a = -1 - 12 ⇒ a = -13. Now, ⇒ an = a + (n - 1)d ⇒ an = -13 + (n - 1)2 = -13 + 2n - 2 = 2n - 15. Hence, option 4 is the correct option.

Mathematics

The 7th term of an A.P. is −1 and its 16th term is 17. The nth term of the A.P. is :
(3n + 12)
(2n − 5)
(3n + 5)
(2n − 15)

AP

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Mathematics

The 7th term of an A.P. is −1 and its 16th term is 17. The nth term of the A.P. is :(3n + 12)(2n − 5)(3n + 5)(2n − 15)

AP

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The 7th term of an A.P. is −1 and its 16th term is 17. The nth term of the A.P. is :
(3n + 12)
(2n − 5)
(3n + 5)
(2n − 15)

There are total 9 terms in an A.P. If the last term and the sum of all the terms are 28 and 144 respectively, then the first term is :
1
7
4
5

The 5th term of an A.P. is −3 and its common difference is −4. The sum of its first 10 terms is :
−50
−40
−60
−30

If the sum of first p terms of an A.P. is ap² + bp, then its common difference is :
a
3a + b
a + b
2a