https://img715.imageshack.us/img715/...at30102012.png

x=4-√x ise x(5+√x)=?

(4-√x).(5+√x)
(4-√x).(4+√x+1)
(16-x+4-√x)
(20-x-(4-x))
(20-4-x+x)
(16)