= 1-1/3 + 1/3-1/5+.......+1/97-1/99
= 1 - 1/99
= 98/99
sao lại là 1- 1/3 + 1/3 -1/5 + ...... 1/97 - 1/99 hả bạn :|
\(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+.....+\frac{2}{95.97}\)\(+\frac{2}{97.99}\)
\(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-....-\frac{1}{97}+\frac{1}{97}-\frac{1}{99}\)
\(=1-\frac{1}{99}\)
\(=\frac{98}{99}\)
vu dinh dat
ta có công thức tổng quát
a/n
\(\frac{2}{1\cdot3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{95\cdot97}+\frac{2}{97\cdot99}\)
\(=\)\(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{95}-\frac{1}{97}+\frac{1}{97}-\frac{1}{99}\)
\(=\)\(1-\frac{1}{99}\)
\(=\)\(\frac{98}{99}\)
= 1-1/3 + 1/3-1/5+...+1/97-1/99
= 1 - 1/99
= 98/99
# hok tốt #
=1/1x3+1/3x5+1/5x7+......+1/95x97+1/97x99
=1/1-1/3+1/3-1/5+1/5-1/7+....+1/95-1/97+1/97-1/99
=1/1-1/99
=98/99
:)))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))
