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8. Sequences and Series
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If ${a^{1/x}} = {b^{1/y}} = {c^{1/z}}$ and $a,\;b,\;c$ are in $G.P.$, then $x,\;y,\;z$ will be in
A
$A.P.$
B
$G.P.$
C
$H.P.$
D
None of these
(IIT-1969)
Solution
(a) Let ${a^{1/x}} = {b^{1/y}} = {c^{1/z}} = k$
$\Rightarrow a = {k^x},\,b = {k^y},\;c = {k^z}$
Now, $a,\;b,\;c$are in $G.P.$
$ \Rightarrow $ ${b^2} = ac $
$\Rightarrow {k^{2y}} = {k^x}.{k^z} = {k^{x + z}} $
$\Rightarrow 2y = x + z$
$ \Rightarrow $ $x,\;y,\;z$ are in $A.P.$
Standard 11
Mathematics