A) x+1/12=-3/8 b) -2=-5/9 c) 2/15-x=-3/10 d) -x+4/5=1/2 e) x.(-3/7)=5/21 f) 14/9.x=28/9 l) x:(-2/5)=-15/16 m) -4/5:x=-2/5 n) x+1/3=2/5-(-1/3) i) 3/7-x=1/4-(-3/5)
A) x+1/12=-3/8 b) -2=-5/9 c) 2/15-x=-3/10 d) -x+4/5=1/2 e) x.(-3/7)=5/21 f) 14/9.x=28/9 l) x:(-2/5)=-15/16 m) -4/5:x=-2/5 n) x+1/3=2/5-(-1/3) i) 3/7-x=1/4-(-3/5)
Đáp án:
$\begin{array}{l}
a)x + \dfrac{1}{{12}} = – \dfrac{3}{8}\\
\Rightarrow x = – \dfrac{3}{8} – \dfrac{1}{{12}}\\
\Rightarrow x = \dfrac{{ – 9 – 2}}{{24}}\\
\Rightarrow x = – \dfrac{{11}}{{24}}\\
b)\text{thiếu}\,\text{đề}\\
c)\dfrac{2}{{15}} – x = \dfrac{{ – 3}}{{10}}\\
\Rightarrow x = \dfrac{2}{{15}} – \left( { – \dfrac{3}{{10}}} \right)\\
\Rightarrow x = \dfrac{2}{{15}} + \dfrac{3}{{10}}\\
\Rightarrow x = \dfrac{{4 + 9}}{{30}}\\
\Rightarrow x = \dfrac{{13}}{{30}}\\
d) – x + \dfrac{4}{5} = \dfrac{1}{2}\\
\Rightarrow x = \dfrac{4}{5} – \dfrac{1}{2}\\
\Rightarrow x = \dfrac{3}{{10}}\\
e)x.\left( { – \dfrac{3}{7}} \right) = \dfrac{5}{{21}}\\
\Rightarrow x = \dfrac{5}{{21}}.\dfrac{{ – 7}}{3}\\
\Rightarrow x = \dfrac{{ – 5}}{9}\\
f)\dfrac{{14}}{9}.x = \dfrac{{28}}{9}\\
\Rightarrow x = \dfrac{{28}}{9}.\dfrac{9}{{14}}\\
\Rightarrow x = 2\\
l)x:\left( { – \dfrac{2}{5}} \right) = \dfrac{{ – 15}}{{16}}\\
\Rightarrow x = \dfrac{{ – 15}}{{16}}.\left( { – \dfrac{2}{5}} \right)\\
\Rightarrow x = \dfrac{3}{8}\\
m) – \dfrac{4}{5}:x = – \dfrac{2}{5}\\
\Rightarrow x = – \dfrac{4}{5}:\left( { – \dfrac{2}{5}} \right)\\
\Rightarrow x = \dfrac{{ – 4}}{5}.\dfrac{5}{{ – 2}}\\
\Rightarrow x = 2\\
n)x + \dfrac{1}{3} = \dfrac{2}{5} – \left( { – \dfrac{1}{3}} \right)\\
\Rightarrow x = \dfrac{2}{5} + \dfrac{1}{3} – \dfrac{1}{3}\\
\Rightarrow x = \dfrac{2}{5}\\
i)\dfrac{3}{7} – x = \dfrac{1}{4} – \left( { – \dfrac{3}{5}} \right)\\
\Rightarrow x = \dfrac{3}{7} – \dfrac{1}{4} – \dfrac{3}{5}\\
\Rightarrow x = \dfrac{{60 – 35 – 3.28}}{{140}}\\
\Rightarrow x = \dfrac{{ – 49}}{{140}} = \dfrac{{ – 7}}{{20}}
\end{array}$