(d) -1\(x\) = log2a a = \(rac{ ext{log}\,a}{ ext{log}\,2a}\), y = log3a 2a = \(rac{ ext{log}\,2a}{ ext{log}\,3a}\)z = log4a 3a = \(rac{ ext{log}\,3a}{ ext{log}\,4a}\)∴ xyz - 2yz = \(rac{ ext{log}\,a}{ ext{log}\,2a}\).\(rac{ ext{log}\,2a}{ ext{log}\,3a}\).\(rac{ ext{log}\,3a}{ ext{log}\,4a}\) - 2\(rac{ ext{log}\,2a}{ ext{log}\,3a}\).\(rac{ ext{log}\,3a}{ ext{log}\,4a}\)= \(rac{ ext{log}\,a}{ ext{log}\,4a}\) - 2\(rac{ ext{log}\,2a}{ ext{log}\,4a}\) = \(rac{ ext{log}\,a-2\, ext{log}\,2a}{ ext{log}\,4a}\)= \(rac{ ext{log}\,a-\, ext{log}\,(2a^2)}{ ext{log}\,4a}\) = \(rac{ ext{log}rac{a}{4}a^2}{ ext{log}\,4a}\) = \(rac{ ext{log}\,(4a)^{-1}}{ ext{log}\,(4a)}\) = \(rac{-1. ext{log}\,4a}{ ext{log}\,4a}\) = -1.