x → T Σ 0 − 1 x → = x → T Σ 1 − 1 x → {\displaystyle {\vec {x}}^{T}\Sigma _{0}^{-1}{\vec {x}}={\vec {x}}^{T}\Sigma _{1}^{-1}{\vec {x}}} x → T Σ i − 1 μ i → = μ i → T Σ i − 1 x → {\displaystyle {\vec {x}}^{T}{\Sigma _{i}}^{-1}{\vec {\mu _{i}}}={\vec {\mu _{i}}}^{T}{\Sigma _{i}}^{-1}{\vec {x}}} because Σ i {\displaystyle \Sigma _{i}} is Hermitian