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If a, b, c are in A.P. and a, b, d are in G.P., then prove that a, a – b, d – c are in G.P. |
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Answer» a, b, c are in AP So, 2b = a + c …(1) b, c, d are in GP So, b2 = ad …(2) Multiply first equation with a and subtract it from 2nd. b2 – 2ab = ad – ac – a2 a2 + b2 – 2ab = a(d – c) ⇒ (a – b)2 = a(d – c) As a, (a – b), (d – c) satisfy the geometric mean relationship Hence a, (a – b),(d – c) are in G.P. |
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