Question

lg 1 supra 2+lg de 2 supra 3 + lg de 3 supra 4 +...+ lg de 99supra 100=?

Answer 1

Stim ca lg a - lg b = lg$\frac{a}{b}$ 
=> (lg1-lg2) + (lg2-lg3) + (lg3-lg4) +...+(lg98-lg99) + (lg99-lg100) 
Dupa ce aranjam parantezele vom obtine
lg 1 + (lg2-lg2) + (lg3-lg3) + ... + (lg99-lg99) - lg 100 = lg 1 - lg 100 = lg$\frac{1}{100}$ = lg $100^{-1}$ = lg $10^{-2}$ = -2