Erro ajax toolkit

I am using Visual Studio 2012 profession  , i used NuGet to install ajax toolkit 4.5

after using Accordion example from microsoft web site

http://www.asp.net/ajaxlibrary/act_Accordion_Simple.ashx

i have the following error when press F12 in Firefox

  AjaxControlToolkit requires ASP.NET Ajax 4.0 scripts. Ensure the correct version of the scripts are referenced. If you are using an ASP.NET ScriptManager, switch to the ToolkitScriptManager in AjaxControlToolkit.dll.