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\(\dfrac{x}{6}=\dfrac{3}{5}+\dfrac{\left(-17\right)}{30}< =>\dfrac{5x}{30}=\dfrac{18}{30}+\dfrac{\left(-17\right)}{30}=>5x=18-17=1< =>x=\dfrac{1}{5}\)
a/ \(\dfrac{-5}{x}\) = \(\dfrac{-18}{72}\)
\(\Rightarrow\dfrac{5}{x}=\dfrac{18}{72}=\dfrac{1}{4}\)
\(\Rightarrow x=5:\dfrac{1}{4}=20\)
\(\dfrac{y}{16}=\dfrac{-18}{72}\) \(=\dfrac{-1}{4}\)
\(\Leftrightarrow\) 4y = - 16
\(\Leftrightarrow\) y = -4
Vậy x = 20 ; y = -4
b/ \(\dfrac{1}{2}=\dfrac{x-1}{8}=\dfrac{10}{y-5}\)
\(\Rightarrow\dfrac{x-1}{8}=\dfrac{1}{2}\)
\(\Rightarrow\dfrac{x-1}{8}=\dfrac{4}{8}\)
\(\Rightarrow x-1=4\)
\(\Rightarrow\) \(x=4+1\)
\(x=5\)
\(\dfrac{10}{y-5}=\dfrac{1}{2}\)
\(\Rightarrow\dfrac{10}{y-5}=\dfrac{10}{20}\)
\(\Rightarrow\) \(y-5=20\)
\(\Rightarrow y=20+5\)
\(y=25\)
Vậy x = 5 ; y = 25
a)
\(-\dfrac{5}{x}=-\dfrac{18}{72}\\ \Leftrightarrow\dfrac{5}{x}=\dfrac{18}{72}=\dfrac{1}{4}\\ \Leftrightarrow x=20\)
\(\dfrac{y}{16}=\dfrac{-18}{72}=-\dfrac{1}{4}\\ \Leftrightarrow4y=-16\\ \Leftrightarrow y=-4\)
b)
\(\dfrac{x-1}{8}=\dfrac{1}{2}\Rightarrow\dfrac{x-1}{8}=\dfrac{4}{8}\Rightarrow x-1=4\Rightarrow x=5\)
\(\dfrac{10}{y-5}=\dfrac{1}{2}\Leftrightarrow y-5=20\Leftrightarrow y=25\)
\(A=\dfrac{-9}{10^{2010}}+\dfrac{-19}{10^{2011}}=\dfrac{-90}{10^{2011}}+\dfrac{-19}{10^{2011}}=\dfrac{\left(-90\right)+\left(-19\right)}{10^{2011}}=\dfrac{-109}{10^{2011}}\)\(B=\dfrac{-9}{10^{2011}}+\dfrac{-19}{10^{2010}}=\dfrac{-9}{10^{2011}}+\dfrac{-190}{10^{2011}}=\dfrac{\left(-9\right)+\left(-190\right)}{10^{2011}}=\dfrac{-199}{10^{2011}}\)\(\text{Vì }\dfrac{-109}{10^{2011}}>\dfrac{-199}{10^{2011}}\text{ nên }A>B\)
\(\dfrac{-5}{x}=\dfrac{y}{16}=\dfrac{-18}{72}\)
=>\(\dfrac{-5}{x}=\dfrac{-18}{72}=>x=\dfrac{72.-5}{-18}=20\)
\(\dfrac{y}{16}=\dfrac{-18}{72}=>y=\dfrac{16.\left(-18\right)}{72}=-4\)
chúc bạn học tốt ^ ^
a)
\(P=\dfrac{5}{6}+\dfrac{5}{12}+\dfrac{5}{20}+\dfrac{5}{30}+\dfrac{5}{42}+\dfrac{5}{56}+\dfrac{5}{72}+\dfrac{5}{90}\\ =\dfrac{5}{2.3}+\dfrac{5}{3.4}+\dfrac{5}{4.5}+\dfrac{5}{5.6}+\dfrac{5}{6.7}+\dfrac{5}{7.8}+\dfrac{5}{8.9}+\dfrac{5}{9.10}\\ \Rightarrow\dfrac{1}{5}P=\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+...+\dfrac{1}{9.10}\\ =\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{9}-\dfrac{1}{10}\\ =\dfrac{1}{2}-\dfrac{1}{10}=\dfrac{5}{10}-\dfrac{1}{10}\\ =\dfrac{4}{10}=\dfrac{2}{5}\\ \Rightarrow P=\dfrac{2}{5}\cdot5=2\)
a: \(=\dfrac{-28}{36}+\dfrac{15}{36}-\dfrac{26}{36}=\dfrac{-39}{36}=\dfrac{-13}{12}\)
b: \(=\dfrac{11}{9}\left(\dfrac{15}{4}-\dfrac{7}{4}-\dfrac{5}{4}\right)=\dfrac{11}{9}\cdot\dfrac{3}{4}=\dfrac{11}{12}\)
c: \(=15+\dfrac{9}{7}+6+\dfrac{2}{3}-5-\dfrac{5}{9}\)
\(=16+\dfrac{88}{63}=\dfrac{1096}{63}\)
d: \(=\dfrac{5}{6}-\dfrac{1}{3}+\dfrac{2}{18}\)
\(=\dfrac{15-6+2}{18}=\dfrac{11}{18}\)
Đề răng dài thế này thì tui giải từng câu hí
a) \(\dfrac{-7}{9}+\dfrac{5}{12}-\dfrac{13}{18}\left(MSC:36\right)\)
\(=\dfrac{-28}{36}+\dfrac{15}{36}-\dfrac{26}{36}\)
\(=\dfrac{-13}{36}-\dfrac{26}{36}\)
\(=\dfrac{-39}{36}\)
\(=\dfrac{13}{3}\)
b) \(\dfrac{11}{9}.\dfrac{15}{4}-\dfrac{11}{4}.\dfrac{7}{9}-\dfrac{11}{9}.\dfrac{5}{4}\)
\(=\left(\dfrac{15}{4}-\dfrac{11}{4}-\dfrac{5}{4}\right).\dfrac{11}{9}\)
\(=\left(1-\dfrac{5}{4}\right).\dfrac{11}{9}\)
\(=\left(\dfrac{4}{4}-\dfrac{5}{4}\right).\dfrac{11}{9}\)
\(=\dfrac{-1}{4}.\dfrac{11}{9}\)
\(=\dfrac{-11}{36}\)
b) \(\dfrac{x}{27}=\dfrac{3}{x}\)
\(\Rightarrow x.x=27.3\)
\(\Rightarrow x^2=81\)
\(\Rightarrow x^2=9^2\)
\(\Rightarrow x=9\)
Vậy x=9
\(\dfrac{-5}{x}=\dfrac{-18}{72}\Rightarrow x.\left(-18\right)=-5.7\)
\(x.\left(-18\right)=-35\)
\(x=-35:\left(-18\right)\)
\(x=\dfrac{35}{18}\)
Vậy \(x=\dfrac{35}{18}\)
- 18 . x = -5 . 72
- 18 .x = -360
x = -360 : -18
x = 20