\(\frac{5}{2.4}+\frac{5}{4.6}+\frac{5}{6.8}+...+\frac{5}{48.50}\)
\(=\frac{5}{2}.\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{48}-\frac{1}{50}\right)\)
\(=\frac{5}{2}.\left(\frac{1}{2}-\frac{1}{50}\right)\)
\(=\frac{5}{2}.\frac{12}{25}\)
\(=\frac{6}{5}\)
Tính : \(\dfrac{5}{2.4}+\dfrac{5}{4.6}+\dfrac{5}{6.8}+...+\dfrac{5}{48.50}\)
Tính tổng: \(S=\frac{1}{1.3}-\frac{1}{2.4}+\frac{1}{3.5}-\frac{1}{4.6}+\frac{1}{5.7}-\frac{1}{6.8}+\frac{1}{7.9}-\frac{1}{8.10}\)
Tính nhanh:
\(\frac{4}{2.4}+\frac{4}{4.6}+...+\frac{4}{98.100}\)
Tính nhanh:
\(\frac{1}{2.4}+\frac{1}{4.6}+...+\frac{1}{98.100}\)
Tìm x:
a)(x+1)2=64
b)\(\frac{9}{2.4}+\frac{9}{4.6}+...+\frac{9}{96.98}+\frac{9}{98.100}\)
rút gọn
a) \(\frac{11^4.6-11^5}{11^4-11^5}\)
b ) \(\frac{9^8.3-3^{18}}{9^8.5+9^8.7}\)
c ) \(\frac{10^5-10^5.3}{10^5.11}\)
Chứng minh rằng: \(\frac{3}{1^2.2^2}+\frac{5}{2^2.3^2}+\frac{7}{3^2.4^2}+...+\frac{19}{9^2.10^2}< 1\)
Giải giúp đi !
S=(1+\(\frac{1}{2.4}\))+(1+\(\frac{1}{3.5}\))+(1+\(\frac{1}{4.6}\))+...+(1+\(\frac{1}{49.51}\))
thực hiện phép tính( tính nhanh nếu có thể)
a/ \(\frac{-7}{25}.\frac{11}{13}+\frac{-7}{25}.\frac{2}{13}-\frac{18}{25}\)
b/ \(\frac{5}{7}.\frac{1}{3}-\frac{5}{7}.\frac{1}{4}-\frac{5}{7}.\frac{1}{12}\)
c/ \(5\frac{2}{5}.4\frac{2}{7}+5\frac{5}{7}.5\frac{2}{5}\)
d/ \(75\%-1\frac{1}{2}+0,5:\frac{5}{12}-\left(\frac{-1}{2}\right)^2\)
