Mathematics
The sum of the 4th term and the 8th term of an A.P. is 24 and the sum of the 6th and 10th term is 44. Find the first three terms of the A.P.
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Answer
Given,
⇒ a4 + a8 = 24
⇒ a + (4 - 1)d + a + (8 - 1)d = 24
⇒ a + 3d + a + 7d = 24
⇒ 2a + 10d = 24 ………(i)
Also,
⇒ a6 + a10 = 44
⇒ a + (6 - 1)d + a + (10 - 1)d = 44
⇒ a + 5d + a + 9d = 44
⇒ 2a + 14d = 44 ………(ii)
Subtracting (i) from (ii) we get,
⇒ 2a + 14d - (2a + 10d) = 44 - 24
⇒ 4d = 20
⇒ d = 5.
Substituting value of d in (i) we get,
⇒ 2a + 10(5) = 24
⇒ 2a = 24 - 50
⇒ 2a = -26
⇒ a = -13
First three terms of A.P. = a, a + d, a + 2d.
= -13, -13 + 5, -13 + 2(5)
Hence, the first three terms of A.P. are -13, -8, -3.
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