The 14th term of an A.P is twice its 8th term. If the 6th term is-8, t – InterviewSolution

1.

The 14th term of an A.P is twice its 8th term. If the 6th term is-8, then find the sumof its first 20 terms

Answer»

A+ 13 d = 2(a+7d)

a + 13d= 2a+ 14d

-a -d = 0

a+ d = 0 = a2 ---- --------> 1a + 5d = -8 -----> 22-1

a +5d = -8a +. d = 0------------------a = 2D = -2

a 20 = 2+ 19*-2 = -36

S20 = 10(2+(-36)) = -340

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