Ta có :
\(B=\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right).....\left(1-\frac{1}{2003}\right)\left(1-\frac{1}{2004}\right)\)
\(B=\frac{1}{2}.\frac{2}{3}.....\frac{2002}{2003}.\frac{2003}{2004}\)
\(B=\frac{1.2.....2002.2003}{2.3.....2003.2004}\)
\(B=\frac{1}{2004}\)
Vậy \(B=\frac{1}{2004}\)
Chúc bạn học tốt ~
B= 1/2.2/3.3/4......2002/2003.2003/2004=1/2004