If ln(a+c) , ln(a-c) , ln(a-2b+c) are in A.P, then
A
a,b,c are in A.P.
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B
a2,b2,c2 are in A.P.
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C
a,b,c are in G.P.
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D
a,b,c are in H.P.
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Solution
The correct option is D
a,b,c are in H.P.
In(a+c),ln(a−c),ln(a−2b+c)areinA.P.⇒a+c,a−c,a−2b+careinG.P.⇒(c−a)2=(a+c)(a−2b+c)⇒(c−a)2=(a+c)2−2b(a+c)⇒2b(a+c)=(a+c)2−(c−a)2⇒2b(a+c)=4ac⇒b=2aca+c a,b,c are in H.P.