[161616/121212+12036/21063]*7
ai nhanh mình tick cho
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\(\subset\frac{161616}{212121}+\frac{12036}{21063}\supset\times7\)
\(\subset\frac{161616:10101}{212121:10101}+\frac{12036:1003}{21063:1003}\supset\times7\)
\(\subset\frac{16}{21}+\frac{12}{21}\supset\times7\)
\(\frac{28}{21}\times7\)
\(\frac{196}{21}\)
\(\frac{28}{3}\)
tick đó nha
\(\dfrac{8}{3}-\dfrac{5}{7}=\dfrac{8\times7}{3\times7}-\dfrac{5\times3}{7\times3}=\dfrac{56}{21}-\dfrac{15}{21}=\dfrac{56-15}{21}=\dfrac{41}{21}\)
\(\dfrac{8}{3}-\dfrac{5}{7}=\dfrac{56}{21}-\dfrac{15}{21}=\dfrac{56-15}{21}=\dfrac{41}{21}\)
\(\frac{121212}{161616}-\left(\frac{151515}{323232}-x\right)=2\)
=> \(\frac{3}{4}-\left(\frac{15}{32}-x\right)=2\)
=> \(\frac{15}{32}-x=\frac{3}{4}-2\)
=> \(\frac{15}{32}-x=-\frac{5}{4}\)
=> \(x=\frac{15}{32}-\frac{-5}{4}=\frac{15}{32}+\frac{5}{4}=\frac{55}{32}\)
b) \(\frac{x}{2}+\frac{x}{6}+\frac{x}{12}+\frac{x}{20}+\frac{x}{30}+\frac{x}{42}+\frac{x}{56}+\frac{x}{72}+\frac{x}{90}=\frac{9}{5}\)
=> \(\frac{x}{1\cdot2}+\frac{x}{2\cdot3}+\frac{x}{3\cdot4}+\frac{x}{4\cdot5}+\frac{x}{5\cdot6}+\frac{x}{6\cdot7}+\frac{x}{7\cdot8}+\frac{x}{8\cdot9}+\frac{x}{9\cdot10}=\frac{9}{5}\)
=> \(\frac{x}{1}-\frac{x}{2}+\frac{x}{2}-\frac{x}{3}+...+\frac{x}{9}-\frac{x}{10}=\frac{9}{5}\)
=> \(\frac{x}{1}-\frac{x}{10}=\frac{9}{5}\)
=> \(\frac{10x-x}{10}=\frac{9}{5}\)
=> \(\frac{9x}{10}=\frac{9}{5}\)
=> \(\frac{9x}{10}=\frac{9\cdot2}{5\cdot2}=\frac{18}{10}\)
=> x = 2
\(\frac{121212}{151515}+\frac{121212}{353535}+\frac{121212}{636363}+\frac{121212}{999999}\)
= \(\frac{12.10101}{15.10101}+\frac{12.10101}{35.10101}+\frac{12.10101}{63.10101}+\frac{12.10101}{99.10101}\)
= \(\frac{12}{15}+\frac{12}{35}+\frac{12}{63}+\frac{12}{99}\)
= \(\frac{12}{3.5}+\frac{12}{5.7}+\frac{12}{7.9}+\frac{12}{9.11}\)
= \(6.\left(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}\right)\)
= \(6.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\right)\)
= \(6.\left(\frac{1}{3}-\frac{1}{11}\right)\)
= \(6.\frac{8}{33}\)
= \(\frac{16}{11}\)
\(B=\left(\frac{15}{16}+\frac{1}{17}\right)-\left(\frac{15}{16}-\frac{16.11}{17.11}\right)\)
\(B=\frac{15}{16}+\frac{1}{17}-\frac{15}{16}+\frac{16}{17}\)
\(B=\frac{1}{17}+\frac{16}{17}=\frac{17}{17}=1\)
=(16/12+4/7)*7
=40/21*7
=40/3