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tự giải đi em bài này học sinh trường chị biết giải hết đó:v
Bài 1:
a; \(\dfrac{7}{8}\) + \(x\) = \(\dfrac{4}{7}\)
\(x\) = \(\dfrac{4}{7}\) - \(\dfrac{7}{8}\)
\(x\) = \(\dfrac{32}{56}\) - \(\dfrac{49}{56}\)
\(x=-\) \(\dfrac{49}{56}\)
Vậy \(x=-\dfrac{49}{56}\)
b; 6 - \(x\) = - \(\dfrac{3}{4}\)
\(x\) = 6 + \(\dfrac{3}{4}\)
\(x\) = \(\dfrac{24}{4}+\dfrac{3}{4}\)
\(x=\dfrac{27}{4}\)
Vậy \(x=\dfrac{27}{4}\)
c; \(\dfrac{1}{-5}\) + \(x\) = \(\dfrac{3}{4}\)
\(x\) = \(\dfrac{3}{4}\) + \(\dfrac{1}{5}\)
\(x=\dfrac{15}{20}\) + \(\dfrac{4}{20}\)
\(x=\dfrac{19}{20}\)
Vậy \(x=\dfrac{19}{20}\)
Bài 1:
d; - 6 - \(x\) = - \(\dfrac{3}{5}\)
\(x\) = - 6 + \(\dfrac{3}{5}\)
\(x=-\dfrac{30}{5}\) + \(\dfrac{3}{5}\)
\(x=-\dfrac{27}{5}\)
Vậy \(x=-\dfrac{27}{5}\)
e; - \(\dfrac{2}{6}\) + \(x\) = \(\dfrac{5}{7}\)
\(x\) = \(\dfrac{5}{7}\) + \(\dfrac{2}{6}\)
\(x\) = \(\dfrac{15}{21}\) + \(\dfrac{1}{3}\)
\(x=\dfrac{15}{21}\) + \(\dfrac{7}{21}\)
\(x=\dfrac{22}{21}\)
Vậy \(x=\dfrac{22}{21}\)
f; - 8 - \(x\) = - \(\dfrac{5}{3}\)
\(x\) = \(-\dfrac{5}{3}\) + 8
\(x\) = \(\dfrac{-5}{3}\) + \(\dfrac{24}{3}\)
\(x\) = \(\dfrac{-19}{3}\)
Vậy \(x=-\dfrac{19}{3}\)
\(\dfrac{1}{4}+\dfrac{8}{9}\le\dfrac{x}{36}< 1-\left(\dfrac{3}{8}-\dfrac{5}{6}\right)\)
\(\Rightarrow\dfrac{41}{36}\le\dfrac{x}{36}< 1-\left(-\dfrac{11}{24}\right)\)
\(\Rightarrow\dfrac{41}{36}\le\dfrac{x}{36}< 1+\dfrac{11}{24}\)
\(\Rightarrow\dfrac{41}{36}\le\dfrac{x}{36}< \dfrac{35}{24}\)
\(\Rightarrow\dfrac{82}{72}\le\dfrac{2x}{72}< \dfrac{105}{72}\)
\(\Rightarrow82\le2x< 105\)
\(\Rightarrow41\le x< \dfrac{105}{2}\)
\(\dfrac{1}{4}+\dfrac{8}{9}\le\dfrac{x}{36}< 1-\left(\dfrac{3}{8}-\dfrac{5}{6}\right)\)
\(\dfrac{\Leftrightarrow41}{36}\le\dfrac{x}{36}< \dfrac{35}{24}\)
\(\dfrac{\Leftrightarrow82}{72}\le\dfrac{2x}{72}< \dfrac{105}{72}\)
\(\Rightarrow82\le2x< 105\)
\(\Rightarrow x=\left\{41;42;43;44;45;46;47;48;49;50;51;52\right\}\)
Ta có:
\(\dfrac{1}{4}+\dfrac{8}{9}=\dfrac{41}{36}\)
\(1-\left(\dfrac{3}{8}-\dfrac{5}{6}\right)=\dfrac{35}{24}\)
ta lại có:
\(\dfrac{41}{36}=\dfrac{82}{72}\)
\(\dfrac{35}{24}=\dfrac{105}{72}\)
\(\Rightarrow\)82 \(\le\)2x < 105
\(\Rightarrow\)41\(\le\)x<52.5
Vậy 41\(\le\)x<52.5
xy = 2.36 = 3.24 = 6.12 = 8.9 = 9.8 = 72
vậy hai đại lượng x và y trong bảng a là hai đại lượng tỉ lệ nghịch