A drug is injected into a patient and the concentration of the drug in the bloodstream is monitored. The​ drug's concentration,​ y, in milligrams per​ liter, after x hours is modeled by the formula below. The graph of this​ equation, obtained with a graphing​ utility, is shown in the figure in a​ [0,10,1] by​ [0,3,1] viewing rectangle. yequalsStartFraction 3 x Over x squared plus 1 EndFraction