ơia,(1-1/2)x(1-1/3)x(1-1/4)x(1-1/5)x....x(1-1/2003)x(1-1/2004)
=1/2x2/3x3/4x4/5x.......x2002/2003x2004
=$\frac{1x2x3x4x...x2002x2003}{2x3x4x5x....x2003x2004}$
=$\frac{1}{2004}$
b,c=1/8+1/24+1/48+....+1/9800
cx2=$\frac{2}{8}$+$\frac{2}{24}$ +.......+$\frac{1}{9800}$
cx2=$\frac{2}{2x4}$+$\frac{2}{4x6}$+......+$\frac{2}{9800}$
cx2=$\frac{1}{2}$-$\frac{1}{4}$+$\frac{1}{4}$-$\frac{1/6}{y}$+.......+$\frac{`1}{98}$-$\frac{1}{100}$
cx2=$\frac{1}{2}$-$\frac{1}{100}$
cx2=$\frac{49}{100}$
c=$\frac{49}{100}$ :2
C=$\frac{49}{200}$
c,1/2+1/4+1/8+1/16+....+1/512+1/1024
Bx2=1+($\frac{1}{2}$+$\frac{1}{4}$ +$\frac{1}{8}$ +......+$\frac{1}{512}$+$\frac{1}{1024}$)-$\frac{1}{1024}$
Bx2=1+B-$\frac{1}{1024}$
B=1-$\frac{1}{1024}$
B=$\frac{1023}{1024}$
Chúc bạn học tốt<3
