for root k900 u can download vroot and very esay root your phone
http://soft.mgyun.com/files/products/vRoot/1000/2014/1896285696/VRoot_1.7.6.5821_Setup.exe
just enable usb dubbling
http://soft.mgyun.com/files/products/vRoot/1000/2014/1896285696/VRoot_1.7.6.5821_Setup.exe
just enable usb dubbling