Chứng minh: S < \(\frac{1}{10}\).Biết S = \(\frac{2}{10.12}+\frac{2}{12.14}+\frac{2}{14.16}+.....+\frac{2}{98.100}\)
Chứng minh S=\(\dfrac{2}{10.12}\) +\(\dfrac{2}{12.14}\) +\(\dfrac{2}{14.16}\) +...+\(\dfrac{2}{98.100}\) <\(\dfrac{1}{10}\)
Tính:
a) A = 3/10.12 + 3/12.14 +...+ 3/998.1000
b) B = 2/1.4 + 2/4.7 + 2/7.10 +...+ 2/22.25
Tính hợp lí (nếu có thể):
\(\frac{2}{10.12}+\frac{2}{12.14}+\frac{2}{14.16}+...+\frac{2}{48.50}\)
Bài 2: Tính:
\(\frac{1}{10.12}+\frac{1}{12.14}+\frac{1}{14.16}+...+\frac{1}{48.50}\)
82/7.9 . 92/8.10 . 102/9.11 . 112/10.12 . 122/11.13 . 132/12.14 . 142/13.15
A=4/10.12 + 4/12.14 + 4/14.16 + ... + 4/96.98
E = 1 / 2.4 + 1 / 6.8 + 1 / 10.12 + 1 / 12.14 = ?