\(=\dfrac{y}{3-y}+\dfrac{y\left(y+3\right)}{2y+3}\cdot\left(\dfrac{y+3}{y\left(y-3\right)}-\dfrac{y}{\left(y-3\right)\left(y+3\right)}\right)\)
\(=\dfrac{-y}{y-3}+\dfrac{y\left(y+3\right)}{2y+3}\cdot\dfrac{y^2+6y+9-y^2}{y\left(y-3\right)\left(y+3\right)}\)
\(=\dfrac{-y}{y-3}+3=\dfrac{-y+3y-9}{y-3}=\dfrac{2y-9}{y-3}\)
\(D=\dfrac{y}{3-y}+\dfrac{y^2+3y}{2y+3}\left(\dfrac{y+3}{y^2-3y}-\dfrac{y}{y^2-9}\right)\\ =\dfrac{y}{3-y}+\dfrac{y\left(y+3\right)}{2y+3}\left(\dfrac{y+3}{y\left(y-3\right)}-\dfrac{y}{\left(y-3\right)\left(y+3\right)}\right)\\ =\dfrac{y}{3-y}+\dfrac{y\left(y+3\right)}{2y+3}.\dfrac{\left(y+3\right)^2-y^2}{y\left(y-3\right)\left(y+3\right)}\\ =\dfrac{y}{3-y}+\dfrac{y\left(y+3\right).3\left(2y+3\right)}{y\left(y-3\right)\cdot y+3}\\ =\dfrac{y}{3-y}+\dfrac{3}{y-3}\\ =\dfrac{y-3}{3-y}\\ =-1\)
