Đáp án:
77) d. \(x = \dfrac{{25}}{{42}}\)
Giải thích các bước giải:
\(\begin{array}{l}
76)\\
a.5 + \dfrac{5}{{27}} + \dfrac{7}{{23}} + \dfrac{1}{2} - \dfrac{5}{{27}} + \dfrac{{16}}{{23}}\\
= \left( {5 + \dfrac{1}{2}} \right) + \left( {\dfrac{5}{{27}} - \dfrac{5}{{27}}} \right) + \left( {\dfrac{7}{{23}} + \dfrac{{16}}{{23}}} \right)\\
= \dfrac{{11}}{2} + \dfrac{{23}}{{23}}\\
= \dfrac{{11}}{2} + 1 = \dfrac{{13}}{2}\\
b)\dfrac{3}{8}.\left( {27 + \dfrac{1}{5} - 51 - \dfrac{1}{5}} \right) + 19\\
= \dfrac{3}{8}.\left( { - 24} \right) + 19 = 10\\
c.\dfrac{1}{5}\left( {25.\left( { - \dfrac{1}{{25}}} \right) + 1} \right) - 2.\dfrac{1}{4} - \dfrac{1}{2}\\
= \dfrac{1}{5}\left( { - 1 + 1} \right) - \dfrac{1}{2} - \dfrac{1}{2}\\
= - 1\\
d.\left( {35 + \dfrac{1}{6}} \right).\left( { - \dfrac{5}{4}} \right) - \left( {45 + \dfrac{1}{6}} \right).\left( { - \dfrac{5}{4}} \right)\\
= \left( { - \dfrac{5}{4}} \right)\left( {35 + \dfrac{1}{6} - 45 - \dfrac{1}{6}} \right)\\
= \left( { - \dfrac{5}{4}} \right)\left( { - 10} \right) = \dfrac{{25}}{2}\\
77)\\
a.x = - \dfrac{2}{3} - \dfrac{1}{5}\\
\to x = - \dfrac{{13}}{{15}}\\
b.x = \dfrac{4}{9} + \dfrac{5}{8}\\
\to x = \dfrac{{77}}{{72}}\\
c.\dfrac{7}{4}x + \dfrac{3}{2} = - \dfrac{4}{5}\\
\to \dfrac{7}{4}x = - \dfrac{4}{5} - \dfrac{3}{2}\\
\to \dfrac{7}{4}x = - \dfrac{{23}}{{10}}\\
\to x = - \dfrac{{46}}{{35}}\\
d.x.\dfrac{9}{{20}} = \dfrac{{15}}{{56}}\\
\to x = \dfrac{{25}}{{42}}
\end{array}\)
