Câu 4 :
đk : x khác -3/2 ; -3 ; 3
\(\dfrac{x}{3-x}+\dfrac{x\left(x+3\right)}{2x+3}\left(\dfrac{x+3}{x\left(x-3\right)}-\dfrac{x}{x^2-9}\right)\)
\(=\dfrac{2x^2+3x+x\left(9-x^2\right)}{\left(3-x\right)\left(2x+3\right)}\left(\dfrac{\left(x+3\right)^2-x^2}{x\left(x-3\right)\left(x+3\right)}\right)\)
\(=\dfrac{2x^2+12x-x^3}{\left(3-x\right)\left(2x+3\right)}\left(\dfrac{6x+9}{x\left(x-3\right)\left(x+3\right)}\right)=\dfrac{2x^2+12x-x^3}{3-x}.\dfrac{3}{x\left(x-3\right)\left(x+3\right)}\)
\(=\dfrac{6x^2+36x-3x^3}{x\left(9-x^2\right)\left(x-3\right)}\)