If you are specifically referring to "functions", then please understand that equations provided using functional notation should be entered without the functional notation because syntactically "f(x)" is equivalent to "the variable f multiplied by the variable x, in parentheses". 

The phrase "under root" indicates everything under the radical and can be entered either through the software-keyboard (shown below) or entered using exponentials, as in "(x^2 + 5)^(1/2)". 

Some of the function-specific features should be reviewed through Algebrator, so please use one of the following links to obtain a free trial of the program:

Windows: http://www.softmath.com/tr/alg51win-tr-en.exe

Mac: http://www.softmath.com/tr/alg51mac-tr-en.dmg