There are three ways to hide quick launch in SharePoint.
  1. Using Out of Box
  2. Using SharePoint Designer
  3. Using CSS
Using Out of Box
Go to Site Settings -> Navigation Elements, and uncheck the "Enable Quick Launch" box.

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Using SharePoint Designer

Open SharePoint Designer, click on Home, and disable the "Quick Launch" checkbox.
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Using CSS
Add Webpart->Media and Content-> Add Script Editor Webpart.

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Edit the Webpart -> Edit Snipped -> Embed the code over here.

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  1. <style type="text/css">
  2. #sideNavBox {DISPLAY: none}
  3. #contentBox {MARGIN-LEFT: 5px}
  4. </style>
This is the final result.

SharePoint
Please try it, and let me know if you are having any problems.