\(E=\dfrac{0.5}{1.2}+\dfrac{0.5}{2\cdot3}+...+\dfrac{0.5}{199\cdot200}\)
\(=\dfrac{1}{2}\left(1-\dfrac{1}{200}\right)\)
\(=\dfrac{1}{2}\cdot\dfrac{199}{200}=\dfrac{199}{400}\)
B= \(\dfrac{1}{1x2}\)+\(\dfrac{1}{2x3}\)+\(\dfrac{1}{3x4}\)+.....+\(\dfrac{1}{198x199}\)+\(\dfrac{1}{199x200}\)
D=\(\dfrac{5}{1x2}\)+\(\dfrac{5}{2x3}\)+\(\dfrac{5}{3x4}\)+....+\(\dfrac{5}{199x200}\)
H=\(\dfrac{0,25}{1x2}\)+\(\dfrac{0,25}{2x3}\)+......+\(\dfrac{0,25}{199x200}\)
(\(1\dfrac{2}{9}\) +\(\dfrac{11}{6}\) )x \(\dfrac{27}{11}\) - 0,5
Bài 3: Tính nhanh
B, (\(\dfrac{1}{4}\)- 0,5 x 0,5) : ( 8,1 + 9,1 + 10,1 +..................+ 20,1)
Tính giá trị biểu thức:
\(\dfrac{1}{2}\) : 0,5 - \(\dfrac{1}{4}\) : 0,25 + \(\dfrac{1}{8}\) : 0,125 - \(\dfrac{1}{10}\) : 0,1
1. Tìm y :
Y x 7:5 + 4x 8 = 134
2. Tính nhanh
\(\dfrac{1}{4}\): 0,25 - \(\dfrac{1}{8}\) : 0,125 + \(\dfrac{1}{2}\) : 0,5 -\(\dfrac{1}{10}\)
C=\(\dfrac{2}{1x2}\)+\(\dfrac{2}{2x3}\)+\(\dfrac{2}{3x4}\)+...+\(\dfrac{2}{2018x2019}\)+\(\dfrac{2}{2019x2020}\)
