bài 1.
\(\dfrac{3}{5};\dfrac{-5}{12};\dfrac{11}{15}\)
\(\dfrac{3}{5}=\dfrac{36}{60};\dfrac{-5}{12}=\dfrac{-25}{60};\dfrac{11}{15}=\dfrac{44}{60}\)
2.
a.\(\dfrac{x}{20}=\dfrac{-12}{20}\Rightarrow x=-12\)
b.\(\dfrac{\left(x-2\right).3}{10.3}=\dfrac{3.2}{15.2}\Leftrightarrow\dfrac{3x-6}{30}=\dfrac{6}{30}\Leftrightarrow3x-6=6\Leftrightarrow3x=12\Rightarrow x=4\)
c.\(\dfrac{5}{40}\le\dfrac{x}{40}< \dfrac{8}{40}\Leftrightarrow5\le x< 8\Rightarrow x=5,6,7\)
Bài 1:
Thu gọn: \(-\dfrac{10}{24}=\dfrac{-10:2}{24:2}=-\dfrac{5}{12}\)
Quy đồng: \(\dfrac{3}{5}=\dfrac{3.12}{5.12}=\dfrac{36}{60};-\dfrac{5}{12}=\dfrac{-5.5}{12.5}=-\dfrac{25}{60};\dfrac{11}{15}=\dfrac{11.4}{15.4}=\dfrac{44}{60}\)
Bài 2:
a) \(\dfrac{x}{20}=-\dfrac{3}{5}\)
\(\Rightarrow x=\dfrac{-20.3}{5}=-12\)
Vậy: \(x=-12\)
b) \(\dfrac{x-2}{10}=\dfrac{3}{15}\)
\(\Rightarrow x-2=\dfrac{10.3}{15}=2\)
\(\Rightarrow x=4\)
Vậy: \(x=4\)
c) \(\dfrac{1}{8}\le\dfrac{x}{40}< \dfrac{1}{5}\)
\(\Rightarrow\dfrac{5}{40}\le\dfrac{x}{40}< \dfrac{8}{40}\)
\(\Rightarrow5\le x< 8\)
\(\Rightarrow x\in\left\{5;6;7\right\}\)
Vậy: \(x\in\left\{5;6;7\right\}\)
Bài 3:
a) Rút gọn: \(\dfrac{-292929}{333333}=\dfrac{-292929:10101}{333333:10101}=\dfrac{-29}{33};\dfrac{-2929}{3333}=\dfrac{-2929:101}{3333:101}=-\dfrac{29}{33}\)
\(\Rightarrow\dfrac{-292929}{333333}=\dfrac{-2929}{3333}\)
Vậy: \(\dfrac{-292929}{333333}=\dfrac{-2929}{3333}\)
b) \(A=\dfrac{17^{18}+1}{17^{19}+1}\)
\(\Rightarrow17A=\dfrac{17^{19}+17}{17^{19}+1}=1+\dfrac{16}{17^{19}+1}\)
\(B=\dfrac{17^{17}+1}{17^{18}+1}\)
\(\Rightarrow17B=\dfrac{17^{18}+17}{17^{18}+1}=1+\dfrac{16}{17^{18}+1}\)
Vì \(1+\dfrac{16}{17^{19}+1}< 1+\dfrac{16}{17^{18}+1}\) nên \(A< B\)
Vậy: \(A=\dfrac{17^{18}+1}{17^{19}+1}< B=\dfrac{17^{17}+1}{17^{18}+1}\)
Giúp em vs ạ