What is simplify expression (combine like terms) y/y+1 - y/y+3

    y           y
  -  
  y+1       y + 3

LCD = (y + 1)(y + 3):-

so we have
 y(y+3 ) - y(y + 1)        y^2 + 3y - y^2 - y               2y
   =      =        answer
     (y + 1)(y + 3              (y + 1)(y + 3)            (y + 1)(y + 3)

The vertex of the quadratic function is (1.5, -.75)