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9 The sum of 5th and 7th terms of anA.P.is4andthe10thtermis46.FindtheA.P |
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Answer» let the first term be a and common difference be d so 5th term = a+4d 7th term = a+6d so , sum is = 2a+10d = 4.....(1) and 10th term is 46 = a+9d.....(2) now the value of A from eq.2 is.a = 46-9d putting this is eq 1 2(46-9d)+10d = 4 => 92-18d +10d = 4 => 92-8d = 4 so 8d = 88 , d = 88/8 = 11 now a = 46-9(11) = 46-99 = -53 so A.P is -53,-42,-31,-20,-9,2,13.... |
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