由韦达定理:lga+lgb=2,lga×lgb=1/2
lg²(a/b)=(lga-lgb)²=(lga+lgb)²-4lga×lgb=2²-4×(1/2)=4-2=2
∴lg(a/b)=±√2
lg(a/b)²=2lg(a/b)=2×(±√2)=±2√2
由韦达定理:lga+lgb=2,lga×lgb=1/2
lg²(a/b)=(lga-lgb)²=(lga+lgb)²-4lga×lgb=2²-4×(1/2)=4-2=2
∴lg(a/b)=±√2
lg(a/b)²=2lg(a/b)=2×(±√2)=±2√2