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Question -

In an A.P, the first term is 2 and the sum of the first five terms is one-fourth of the next five terms. Show that 20th term is тАУ112.



Answer -

Given,

The first term (a) ofan A.P = 2

LetтАЩs assume┬аd┬аbethe common difference of the A.P.

So, the A.P. will be2, 2 +┬аd, 2 + 2d, 2 + 3d, тАж

Then,

Sum of first fiveterms = 10 + 10d

Sum of next five terms= 10 + 35d

From the question, wehave

10 + 10d = ┬╝ (10 +35d)

40 + 40d = 10 + 35d

30 = -5d

d = -6

a20┬а=a + (20 тАУ 1)d = 2 + (19) (-6) = 2 тАУ 114 = -112

Therefore, the 20th┬аtermof the A.P. is тАУ112.

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