[tex]A= \frac{1}{1.2}[/tex]+[tex]\frac{1}{3.4}[/tex]+[tex]\frac{1}{5.6}[/tex]+...+[tex]\frac{1}{99.100}[/tex] Chứng minh rằng: A < [tex]\frac{5}{6}[/tex] mik cảm ơn!!
Ta có A = 1/1.2 + 1/3.4 + 1/4.5 + .....+1/99.100 = 1 - 1/2 + 1/3 - 1/4 + 1/4 - 1/5 +.......+ 1/99 - 1/100 = 1 - 1/100 = 99/100 Ta có 99/100 < 5/6 Nên A < 5/6