If you don’t want to change show the quick launch section on few pages or sites (i.e Team Site), you need to do a trick with content editor web part, so let’s start.

1.   Add a content editor web part, doesn’t matter where you add it. (Located under “Media and Content” web part categories). 

2.   Select the web part and click “Edit HTML source” from ribbon under the format text tool.

3.   In the HTML source add the following code and click “OK” 

<style>

#s4-leftpanel{
display:none
}
.s4-ca{
margin-left:0px
}

</style>

4.   Save the page. The “quick launch” section should not be visible now as you can see the below pictures.

5.   Now to hide the content editor web part, from the web part properties check the hidden property checkbox. 

6.   This trick works on any SharePoint 2010 or Foundation site or pages.