$ sudo rpm -ivh VirtualBox-5.1-5.1.14_112924_fedora24-1.x86_64.rpm
warning: VirtualBox-5.1-5.1.14_112924_fedora24-1.x86_64.rpm: Header V4 DSA/SHA1 Signature, key ID 98ab5139: NOKEY
error: Failed dependencies:
    libQt5X11Extras.so.5()(64bit) is needed by VirtualBox-5.1-5.1.14_112924_fedora24-1.x86_64
    libQt5X11Extras.so.5(Qt_5)(64bit) is needed by VirtualBox-5.1-5.1.14_112924_fedora24-1.x86_64

【解决办法】

手动安装依赖项qt5-qtx11extras：

$ sudo dnf install qt5-qtx11extras
Last metadata expiration check: 0:01:22 ago on Sun Jan 29 13:08:42 2017.
Dependencies resolved.
================================================================================
 Package                Arch          Version              Repository      Size
================================================================================
Installing:
 qt5-qtx11extras        x86_64        5.6.2-1.fc24         updates         28 k

Transaction Summary
================================================================================
Install  1 Package

Total download size: 28 k
Installed size: 51 k
Is this ok [y/N]: y
Downloading Packages:
qt5-qtx11extras-5.6.2-1.fc24.x86_64.rpm          60 kB/s |  28 kB     00:00   
--------------------------------------------------------------------------------
Total                                            13 kB/s |  28 kB     00:02    
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Installing  : qt5-qtx11extras-5.6.2-1.fc24.x86_64                         1/1
  Verifying   : qt5-qtx11extras-5.6.2-1.fc24.x86_64                         1/1

Installed:
  qt5-qtx11extras.x86_64 5.6.2-1.fc24                                           

Complete!

不要直接安装提示中所说的libQt5X11Extras软件包，因为软件源里没有：

$ sudo dnf install libQt5X11Extras
Fedora 24 - x86_64 - Updates                    1.1 MB/s |  21 MB     00:19   
Last metadata expiration check: 0:00:22 ago on Sun Jan 29 13:08:42 2017.
No package libQt5X11Extras available.
Error: Unable to find a match.

然后就可以安装VirtualBox了：

$ sudo rpm -ivh VirtualBox-5.1-5.1.14_112924_fedora24-1.x86_64.rpm
warning: VirtualBox-5.1-5.1.14_112924_fedora24-1.x86_64.rpm: Header V4 DSA/SHA1 Signature, key ID 98ab5139: NOKEY
Preparing...                          ################################# [100%]
Updating / installing...
   1:VirtualBox-5.1-5.1.14_112924_fedo################################# [100%]

Creating group 'vboxusers'. VM users must be member of that group!