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If the 2nd , 5th and 9th terms of a non –constant A.P. are in G.P., then the common ratio of  this G.P is

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a
74
b
85
c
43
d
1

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detailed solution

Correct option is C

a+d,a+4d, a+8d are in G.P.⇒a+4d2=a+da+8d⇒a2+16d2+8da=a2+9ad+8d2⇒8d2−ad=0⇒d(8d−a)=0⇒a=8d∴r=a+4da+d=12d9d=43


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If the roots of the equation, x3+px2+qx1=0  form an increasing G.P., where pandq  are real, then


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