lga+lgb = lg(a*b)lga-lgb = lg(a/b)lg500+1g8/5-1/2lg64+50(lg2+lg5)²= lg(500*8/5)-lg(根号(64))+50(lg(2*5))^2= lg(800)-lg(8) + 50*(lg(10))^2= lg(800/8) + 50= lg(100) + 50= 2+50= 52