[tex]\displaystyle \frac{5y^2}{1-y^2}:(1-\frac{1}{1-y})=\frac{5y^2}{1-y^2}:\frac{1-y-1}{1-y}=\frac{5y^2}{1-y^2}:\frac{-y}{1-y}=\frac{5y^2}{1-y^2}*\frac{1-y}{-y}=\\\\\frac{5y^2}{1-y^2}*(-\frac{1-y}{y})=-\frac{5y}{(1-y)(1+y)}*(1-y)=-\frac{5y}{1+y}[/tex]