Question

срочно дам балы прошу пожалуйста

Answer 1

$\frac{1-y\sqrt5}{1+y\sqrt5}+\frac{1+y\sqrt5}{1-y\sqrt5}=\frac{9y}{1-5y^2}\; \; ,\; \; ODZ:\; \; y\ne \pm \frac{1}{\sqrt5}\\\\\frac{(1-y\sqrt5)^2+(1+y\sqrt5)^2}{(1+y\sqrt5)(1-\sqrt5)}=\frac{9y}{(1-y\sqrt5)(1+y\sqrt5)}\\\\\frac{1-2y\sqrt5+5y^2+1+2y\sqrt5+5y^2}{(1+y\sqrt5)(1+y\sqrt5)}=\frac{9y}{(1-y\sqrt5)(1+y\sqrt5)}\\\\2+10y^2=9y\\\\10y^2-9y+2=0\; \; ,\; \; D=9^2-80=1\\\\y_1=\frac{9-1}{20}=\frac{2}{5}=0,4\; \; ,\; \; y_2=\frac{10}{20}=0,5\\\\Otvet:\; \; y=0,4\; \; ,\; \; y=0,5\; .$