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.