Giải các phương trình sau: a, (x-3/5 +1)/4=(2x/3 -1/2)/6 b, (5x +x+2/2)/9 -x=(x+3/5 +15)/12 -2

Đáp án:

 a) x=3

Giải thích các bước giải:

\(\begin{array}{l}
a)\left( {\dfrac{{x – 3}}{5} + 1} \right):4 = \left( {\dfrac{{2x}}{3} – \dfrac{1}{2}} \right):6\\
 \to \left( {\dfrac{{x – 3 + 5}}{5}} \right).\dfrac{1}{4} = \left( {\dfrac{{4x – 3}}{6}} \right).\dfrac{1}{6}\\
 \to \dfrac{{x + 2}}{{20}} = \dfrac{{4x – 3}}{{36}}\\
 \to 36x + 72 = 80x – 60\\
 \to 44x = 132\\
 \to x = 3\\
b)\left( {5x + \dfrac{{x + 2}}{2}} \right):9 – x = \left( {\dfrac{{x + 3}}{5} + 15} \right):12 – 2\\
 \to \dfrac{{10x + x + 2}}{2}.\dfrac{1}{9} – x = \dfrac{{x + 3 + 75}}{5}.\dfrac{1}{{12}} – 2\\
 \to \dfrac{{11x + 2}}{{18}} – x = \dfrac{{x + 78}}{{60}} – 2\\
 \to \dfrac{{11x + 2 – 18x}}{{18}} = \dfrac{{x + 78 – 120}}{{60}}\\
 \to \dfrac{{2 – 6x}}{{18}} = \dfrac{{x – 42}}{{60}}\\
 \to 120 – 360x = 18x – 756\\
 \to 378x = 876\\
 \to x = \dfrac{{146}}{{63}}
\end{array}\)