b) ( 1- \(\dfrac{1}{2}\) ) . ( 1 - \(\dfrac{1}{3}\) ) . ( 1 - \(\dfrac{1}{4}\) ) ... ( 1 - \(\dfrac{1}{x}\) ) = 0,01
\(\Rightarrow\) \(\dfrac{1}{2}\) . \(\dfrac{2}{3}\) . \(\dfrac{3}{4}\) ... \(\dfrac{x-1}{x}\) = 0,01
\(\Rightarrow\) \(\dfrac{1.2.3...\left(x-1\right)}{2.3.4...x}\) = 0,01
\(\Rightarrow\) \(\dfrac{1}{x}\) = 0,01
\(\Rightarrow\) \(\dfrac{1}{x}\) = \(\dfrac{1}{100}\)
\(\Rightarrow\) x = 100
Vậy x =100
=>1/2*2/3*...*(x-1)/x=1/100
=>1/x=1/100
=>x=100