Выражение: y+3/2y+3 * (y+3/y-3 + y^2/9-y^2)

В скобках

(y+3)/(y-3) -y²/(y-3)(y+3) =

=((y+3)(y+3) -y²) /(y-3)(y+3) =

=(y²+6y+9 -y²) /(y-3)(y+3) =

=(3(2y+3)) /(y-3)(y+3)

умножение

((y+3)*3(2y+3)) /(2y+3)*(y-3)(y+3) =

=3 /(y-3)