Q. 535.0( 1 Vote )

Find four numbers forming a Geometric progression in which the third term is greater than the first by 9, and the second term is greater than the fourth by 18.



Answer :


The four terms of G.P are a, ar, ar2, ar3.

ar2 - a = 9

a (r2-1) = 9 ………..(1)

ar (1 - r2) = 18 ……..(2)

Dividing (2) by (1)





r = -2

Substitute r in (1)

a (4-1) = 9

a = 3

... the four numbers are 3, 3(-2), 3(-2)2 and 3(-2)3

(i.e) 3, -6, 12, -24.

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