(lgα)2-lgα2-2=0
(lgβ)2-lgβ2-2=0
两式相减(lgα+lgβ)(lgα-lgβ)-2(lgα-lgβ)=0
(lgα+lgβ-2)(lgα-lgβ)=0
lgα+lgβ-2=0
logαβ=lgα+lgβ=2