It is the square root of 15/2 or the square root of 7.5, which is approximately 2.74.
The first one is an odd function
The second one is neither of them, because the only function which is even and odd at the same time is f(x) =0
The third one is an even one
Divide both sides by 2. what you do to one side you have to do to the other so in this case it would be: i<3u