\(\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+...+\frac{2}{2014.2016}=1-\frac{2}{4}+\frac{2}{4}-\frac{2}{6}+\frac{2}{6}-\frac{2}{8}+...+\frac{2}{2014}-\frac{2}{2016}\)
\(=1-\frac{2}{2016}=\frac{1007}{1008}\)
Tính nhanh:
A=\(\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}+\frac{1}{6\cdot7}+\frac{1}{7\cdot8}\)
Tính (theo mẫu)
Mẫu:\(\frac{5\cdot6\cdot7\cdot9}{12\cdot7\cdot27}\)=\(\frac{5\cdot6\cdot7\cdot9}{6\cdot2\cdot7\cdot9\cdot3}\)=\(\frac{5}{6}\)
a.\(\frac{3\cdot4\cdot7}{12\cdot8\cdot9}\)=.........................................................................
b.\(\frac{4\cdot5\cdot6}{12\cdot10\cdot8}\)=.......................................................................
c\(\frac{5\cdot6\cdot7}{12\cdot14\cdot15}\)=......................................................................
Tính (theo mẫu)
Mẫu:\(\frac{5\cdot6\cdot7\cdot9}{12\cdot7\cdot27}\)=\(\frac{5\cdot6\cdot7\cdot9}{6\cdot2\cdot7\cdot9\cdot3}\)=\(\frac{5}{6}\)
a.\(\frac{3\cdot4\cdot7}{12\cdot8\cdot9}\).............................................
b.\(\frac{4\cdot5\cdot6}{12\cdot10\cdot8}\)...........................................
c.\(\frac{5\cdot6\cdot7}{12\cdot14\cdot15}\)........................................
(Lưu ý:Dấu chấm là dấu nhân)
tính nhanh
a)\(\frac{12\cdot4+12\cdot6}{24}\) b)\(\frac{16\cdot8-16\cdot2}{12\cdot4}\)
\(\frac{1}{3\cdot4}+\frac{1}{4\cdot6}+\frac{1}{6\cdot9}+\frac{1}{9\cdot13}+\frac{1}{13\cdot18}=...\)
Nhập kết quả dưới dạng phân số tối giản
tính
\(\frac{4\cdot5\cdot6}{3\cdot10\cdot8}\)
ghi nhớ dấu chấm là dấu nhân
Tính nhanh:
\(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+.....+\frac{1}{1000\cdot1001}\)
Tính tổng sau bằng cách hợp lí : A = \(\frac{1}{2\cdot5}+\frac{1}{5\cdot8}+\frac{1}{8\cdot11}+...+\frac{1}{17\cdot20}\)
Tính nhanh :
\(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\frac{1}{101\cdot102}\)