a, đk x khác 2 ; 4 ; -3
\(\dfrac{\left(y-1\right)\left(y-4\right)-\left(y-2\right)\left(y-2\right)}{\left(y-2\right)\left(y-4\right)}=\dfrac{3-y}{y+3}\)
\(\Leftrightarrow\left(y-1\right)\left(y-4\right)-\left(y^2-4\right)\left(y+3\right)=\left(3-y\right)\left(y-2\right)\left(y-4\right)\)
\(\Leftrightarrow11y^2-25y+8=0\Leftrightarrow y=\dfrac{25\pm\sqrt{273}}{22}\left(tm\right)\)
b, đk y khác -1/3 ; y khác -3
\(\dfrac{y-1}{3y+1}=\dfrac{3-y}{y+3}+2\Rightarrow y^2+2y-3=9y-3y^2+3-3y+2\left(3y+1\right)\left(y+3\right)\)
\(\Leftrightarrow4y^2-4y-8=2\left(3y^2+10y+3\right)\Leftrightarrow2y^2+24y+14=0\)
\(\Leftrightarrow x=-6\pm\sqrt{29}\)(tm)
