lga,lgb为方程2x^2-4x+1=0两不同实根由韦达定理 lga+lgb=2 lgalgb=1/2lg(b/a)^2 =2lg(b/a) =2(lgb-lga) |lgb-lga|^2=(lgb+lga)^2-4lgalgb =4-4*(1/2)=2 lgb-lga=±√2 则lg(b/a)^2=±2√2