So sánh \(x\) và \(y\) biết rằng:
\(y - \left( {\dfrac{4}{{15}} + \dfrac{1}{5}} \right):\dfrac{4}{9} = \dfrac{5}{8};\)
\(\left( {x + \dfrac{5}{6}} \right) \times \dfrac{{12}}{{25}} = \dfrac{{47}}{{50}}\)
Trả lời bởi giáo viên
B. \(x < y\)
Ta có:
$y - \left( {\dfrac{4}{{15}} + \dfrac{1}{5}} \right):\dfrac{4}{9} = \dfrac{5}{8}$
$y - \dfrac{7}{{15}}:\dfrac{4}{9} = \dfrac{5}{8}$
$y - \dfrac{7}{{15}} \times \dfrac{9}{4} = \dfrac{5}{8}$
$y - \dfrac{{21}}{{20}} = \dfrac{5}{8}$
$y = \dfrac{5}{8} + \dfrac{{21}}{{20}}$
$y = \dfrac{{67}}{{40}}$
+ Lại có
$\left( {x + \dfrac{5}{6}} \right) \times \dfrac{{12}}{{25}} = \dfrac{{47}}{{50}}$
$x + \dfrac{5}{6} = \dfrac{{47}}{{50}}:\dfrac{{12}}{{25}}$
$x + \dfrac{5}{6} = \dfrac{{47}}{{50}} \times \dfrac{{25}}{{12}}$
$x + \dfrac{5}{6} = \dfrac{{47}}{{24}}$
$x = \dfrac{{47}}{{24}} - \dfrac{5}{6}$
$x = \dfrac{9}{8}$
Ta có: \(\dfrac{9}{8} = \dfrac{{9 \times 5}}{{8 \times 5}} = \dfrac{{45}}{{40}}\)
Vì \(\dfrac{{67}}{{40}} > \dfrac{{45}}{{40}}\) nên \(\dfrac{{67}}{{40}} > \dfrac{9}{8}\).
Vậy \(y > x\) hay \(x < y\)
Hướng dẫn giải:
Tìm \(x;\,\,y\) sau đó so sánh hai số đó.