\(C=\frac{2}{4}.\left(\frac{4}{1.5}+\frac{4}{5.9}+\frac{4}{9.13}+\frac{4}{13.17}+\frac{4}{17.21}\right)\)
\(=\frac{1}{2}.\left(1-\frac{1}{5}+\frac{1}{5}-\frac{1}{9}+....+\frac{1}{17}-\frac{1}{21}\right)\)
\(=\frac{1}{2}.\left(1-\frac{1}{21}\right)\)
\(=\frac{1}{2}.\frac{20}{21}\)
\(=\frac{10}{21}\)
\(\left(\frac{2}{11\cdot13}+\frac{2}{13\cdot15}+\frac{2}{15\cdot17}+\frac{2}{17\cdot19}+\frac{2}{19\cdot21}\right)\cdot462-y=19\)
Tính nhanh biểu thức sau :
\(\frac{4}{1\cdot3}+\frac{4}{3\cdot5}+\frac{4}{5\cdot7}+\frac{4}{7\cdot9}+....+\frac{4}{15\cdot17}+\frac{4}{17\cdot19}+\frac{4}{19\cdot21}\)
\(\left(\frac{2}{11\cdot13}+\frac{2}{13\cdot15}+\frac{2}{15\cdot17}+\frac{2}{17\cdot19}+\frac{2}{19\cdot21}\right)\cdot462-y=19\)
dấu chấm thành dấu nhân nha thông cảm
Tính nhanh:
\(\frac{33}{2}+\frac{33}{6}+\frac{33}{18}+\frac{33}{54}+\frac{33}{162}+\frac{33}{486}\)
\(\frac{2}{3\cdot5}+\frac{2}{5\cdot7}+\frac{2}{7\cdot9}+\frac{2}{9\cdot11}+\frac{2}{11\cdot13}+\frac{2}{13\cdot15}\)
Lấy \(\varphi=1,618\); tính \(\frac{\varphi}{1\cdot2}+\frac{\varphi}{2\cdot3}+\frac{\varphi}{3\cdot5}+\frac{\varphi}{5\cdot8}+\frac{\varphi}{8\cdot13}+\frac{\varphi}{13\cdot21}+\frac{\varphi}{21\cdot34}+\frac{\varphi}{34\cdot55}+\frac{\varphi}{55\cdot89}+\frac{\varphi}{89\cdot144}+...\)
\(\frac{4\cdot x}{1\cdot5}\)+ \(\frac{4\cdot x}{5\cdot9}\) + \(\frac{4\cdot x}{9\cdot13}\) + \(\frac{4\cdot x}{13\cdot17}\) = 16
vậy x = ?
ai có cách giải bài này nhanh nhất thì giúp mình với ( dấu chấm ở giũa phép tính là giấu nhân )
\(\frac{2}{1\cdot3}+\frac{2}{3\cdot5}+\frac{2}{5\cdot7}+\frac{2}{7\cdot9}+\frac{2}{9\cdot12}\)
(\(\frac{2}{11\cdot13}+\frac{2}{13\cdot15}+...+\frac{2}{19\cdot21}\)) * 462 - 2,04 : (x+1,5) + 11,02 = 30
Tìm \(x\) biết: \(\left(\frac{1}{3\cdot5}+\frac{1}{5\cdot7}+\frac{1}{7\cdot9}+...+\frac{1}{19\cdot21}\right)\cdot x=\frac{9}{7}\)
