a) \(\dfrac{x-1}{x^2-4}=\dfrac{3}{2-x}\)
\(\Leftrightarrow\dfrac{x-1}{\left(x-2\right)\left(x+2\right)}=-\dfrac{3}{\left(x-2\right)\left(x+2\right)}\)
\(ĐKXĐ:\left\{{}\begin{matrix}x\ne2\\x\ne-2\end{matrix}\right.\)
\(\Rightarrow x-1=-3\)
\(\Leftrightarrow x=1-3=-2\)
Vậy: \(x=-2\)
b) \(\dfrac{1}{x-1}-\dfrac{7}{x-2}=\dfrac{1}{\left(x-1\right)\left(2-x\right)}\)
\(\Leftrightarrow\dfrac{1}{x-1}-\left(-\dfrac{7}{2-x}\right)=\dfrac{1}{\left(x-1\right)\left(2-x\right)}\)
\(ĐKXĐ:\left\{{}\begin{matrix}x\ne1\\x\ne2\end{matrix}\right.\)
\(\Leftrightarrow\dfrac{2-x}{\left(x-1\right)\left(2-x\right)}+\dfrac{7\left(x-1\right)}{\left(x-1\right)\left(2-x\right)}=\dfrac{1}{\left(x-1\right)\left(2-x\right)}\)
\(\Rightarrow2-x+7x-7=1\)
\(\Leftrightarrow-x+7x=1-2+7=6\)
\(\Leftrightarrow6x=6\)
\(\Leftrightarrow x=1\)
Vậy: \(x=1\)
c) \(\dfrac{2x+3}{2x-3}-\dfrac{3}{4x-6}=\dfrac{2}{5}\)
\(\Leftrightarrow\dfrac{2x+3}{2x-3}-\dfrac{3}{2\left(2x-3\right)}=\dfrac{2}{5}\)
\(\Leftrightarrow\dfrac{10\left(2x+3\right)}{10\left(2x-3\right)}-\dfrac{3.5}{10\left(2x-3\right)}=\dfrac{4\left(2x-3\right)}{10\left(2x-3\right)}\)
\(ĐKXĐ:x\ne\dfrac{3}{2}\)
\(\Leftrightarrow10\left(2x+3\right)-15=4\left(2x-3\right)\)
\(\Leftrightarrow20x+30-15=8x-12\)
\(\Leftrightarrow20x-8x=15-12-30\)
\(\Leftrightarrow12x=-27\)
\(\Leftrightarrow x=-\dfrac{27}{12}=-\dfrac{9}{4}\)
Vậy: \(x=-\dfrac{9}{4}\)
d) \(\dfrac{x+29}{31}-\dfrac{x+27}{33}=\dfrac{x+17}{43}-\dfrac{x+15}{45}\)
\(\Leftrightarrow\left(\dfrac{x+29}{31}+1\right)-\left(\dfrac{x+27}{33}+1\right)=\left(\dfrac{x+17}{43}+1\right)-\left(\dfrac{x+15}{45}+1\right)\)
\(\Leftrightarrow\dfrac{x+60}{31}-\dfrac{x+60}{33}=\dfrac{x+60}{43}-\dfrac{x+60}{45}\)
\(\Leftrightarrow\dfrac{x+60}{31}-\dfrac{x+60}{33}-\dfrac{x+60}{43}+\dfrac{x+60}{45}\)
\(\Leftrightarrow\left(x+60\right)\left(\dfrac{1}{31}-\dfrac{1}{33}-\dfrac{1}{43}+\dfrac{1}{45}\right)=0\)
\(\Leftrightarrow x+60=0\) vì \(\left(\dfrac{1}{31}-\dfrac{1}{33}-\dfrac{1}{43}+\dfrac{1}{45}\ne0\right)\)
\(\Leftrightarrow x=-60\)
Vậy: \(x=-60\)
_Good luck to you_
