18.verificați egalitatea lg 2 +lg 3/2 +lg 4/3+...+lg 10/9 =1
19. verificați egalitatea
[tex] log_{2}( \frac{1}{2} ) + log_{2}( \frac{2}{3} ) + log_{2}( \frac{3}{4} ) + .... + log_{2}( \frac{15}{16} ) = - 4[/tex]
20. Calculați
[tex] log_{3}(2) + log_{3}( \frac{3}{2} ) + log_{3}( \frac{4}{3} ) + ... + log_{3}( \frac{27}{26} ) [/tex]
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