Tìm x, biết:
a) (1/1/2 – 25%x – 5/12) – 3x =1,6 : 3/5
b) (-2/3)^2 : (x-1) + 3^1001 .[ 7/4 – (3/2^2 + 1)] = 2/9
c) 1/2 . (4x-6) – 1 = 2. (1/2x + 3)
Tìm x, biết: a) (1/1/2 – 25%x – 5/12) – 3x =1,6 : 3/5 b) (-2/3)^2 : (x-1) + 3^1001 .[ 7/4 – (3/2^2 + 1)] = 2/9 c) 1/2 . (4x-6) – 1 = 2. (1/2x + 3)
By Aaliyah
Đáp án:
$\begin{array}{l}
a)\left( {1\dfrac{1}{2} – 25\% .x – \dfrac{5}{{12}}} \right) – 3x = 1,6:\dfrac{3}{5}\\
\Rightarrow \left( {\dfrac{3}{2} – \dfrac{{25}}{{100}}.x – \dfrac{5}{{12}}} \right) – 3x = \dfrac{{16}}{{10}}.\dfrac{5}{3}\\
\Rightarrow \dfrac{{18}}{{12}} – \dfrac{5}{{12}} – \dfrac{1}{4}x – 3x = \dfrac{8}{3}\\
\Rightarrow \dfrac{{13}}{{12}} + \left( { – \dfrac{1}{4} – 3} \right).x = \dfrac{8}{3}\\
\Rightarrow \left( {\dfrac{{ – 1}}{4} – \dfrac{{12}}{4}} \right).x = \dfrac{8}{3} – \dfrac{{13}}{{12}}\\
\Rightarrow \dfrac{{ – 13}}{4}.x = \dfrac{{32 – 13}}{{12}}\\
\Rightarrow – \dfrac{{13}}{4}.x = \dfrac{{19}}{{12}}\\
\Rightarrow x = \dfrac{{19}}{{12}}.\dfrac{{ – 4}}{{13}}\\
\Rightarrow x = \dfrac{{ – 19}}{{39}}\\
b){\left( { – \dfrac{2}{3}} \right)^2}:\left( {x – 1} \right) + {3^{1001}}.\left( {\dfrac{7}{4} – \left( {\dfrac{3}{{{2^2}}} + 1} \right)} \right) = \dfrac{2}{9}\\
\Rightarrow \dfrac{4}{9}:\left( {x – 1} \right) + {3^{1001}}.\left( {\dfrac{7}{4} – \dfrac{3}{4} – 1} \right) = \dfrac{2}{9}\\
\Rightarrow \dfrac{4}{9}:\left( {x – 1} \right) + {3^{1001}}.\left( {\dfrac{4}{4} – 1} \right) = \dfrac{2}{9}\\
\Rightarrow \dfrac{4}{9}:\left( {x – 1} \right) + {3^{1001}}.0 = \dfrac{2}{9}\\
\Rightarrow \dfrac{4}{9}:\left( {x – 1} \right) = \dfrac{2}{9}\\
\Rightarrow x – 1 = \dfrac{4}{9}:\dfrac{2}{9} = 2\\
\Rightarrow x = 2 + 1 = 3\\
c)\dfrac{1}{2}.\left( {4x – 6} \right) – 1 = 2.\left( {\dfrac{1}{2}x + 3} \right)\\
\Rightarrow \dfrac{1}{2}.4x – \dfrac{1}{2}.6 – 1 = 2.\dfrac{1}{2}x + 2.3\\
\Rightarrow 2x – 3 – 1 = x + 6\\
\Rightarrow 2x – x = 6 + 3 + 1\\
\Rightarrow x = 10
\end{array}$