B = \(\frac{6}{1.3}+\frac{6}{3.5}+...+\frac{6}{97.99}=3.\left(\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{97.99}\right)\)

   =\(3.\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{97}-\frac{1}{99}\right)=3.\left(1-\frac{1}{99}\right)=3.\frac{98}{99}=\frac{98}{33}\)

351 . 96 + 123 = 33819

\(\frac{x}{32}=\frac{2}{x}\)

\(\Rightarrow x^2=32.2=64\)

\(\Rightarrow x^2=8^2=\left(-8\right)^2\)

Vì x là số âm 

=> x = -8