Sửa đề :
\(\frac{12}{3\cdot5}+\frac{12}{5\cdot7}+\frac{12}{7\cdot9}+...+\frac{12}{97\cdot99}\)
\(=\frac{1}{2}\left(\frac{12}{3}-\frac{12}{5}+\frac{12}{5}-\frac{12}{7}+\frac{12}{7}-\frac{12}{9}+...+\frac{12}{97}-\frac{12}{99}\right)\)
\(=\frac{1}{2}\left(\frac{12}{3}-\frac{12}{99}\right)\)
\(=\frac{1}{2}\cdot\frac{128}{33}\)
\(=\frac{64}{33}\)
bài 1:tính
a) \(\frac{5}{1.4}+\frac{5}{4.7}+\frac{5}{7.10}+...+\frac{5}{27.30}\)
b)\(\frac{12}{3.5}+\frac{12}{5.7}+\frac{12}{7.9}+...+\frac{12}{97.90}\)
nhanh lên nha gấp lắm rồi ai làm đúng và nhanh nhất tui tick cho
Tính giá trị biểu thức
\(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+......1\frac{2}{41.43}\)
Tính tổng:
A=\(\frac{2}{3.5}\)+\(\frac{2}{5.7}\)+\(\frac{2}{7.9}\)+........+\(\frac{2}{37.39}\)
giải giúp mình với
\(\frac{1}{1.3}\)+\(\frac{1}{3.5}\)+\(\frac{1}{5.7}\)+\(\frac{1}{7.9}\)=?
Tính tổng :B = \(\frac{1}{2}\) + \(\frac{1}{6}\) + \(\frac{1}{12}\) + \(\frac{1}{20}\) + ba chấm + \(\frac{1}{9900}\)
C = \(\frac{2}{3.5}\) + \(\frac{2}{5.7}\) + ba chấm + \(\frac{2}{2009.2011}\)
Tìm \(x\) :
\(\left(\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}+...+\frac{1}{19.21}\right)\)x \(x\) = \(\frac{9}{7}\)
\(66\frac{5}{12}+36\frac{12}{12}+25\frac{12}{24}\)
\(\frac{7}{12}-\frac{2}{7}+\frac{1}{12}\)
\(\frac{12}{17}-\frac{5}{17}-\frac{4}{17}\)
\(\frac{15-\frac{15}{7}-\frac{15}{12}-\frac{15}{98}}{18-\frac{18}{7}-\frac{18}{12}-\frac{18}{98}}\)
