What Determines the Correct K Value for a Probability Density Function?

[Jason03]

I am tyring to solve the follwing problem...


http://www.imagedump.com/index.cgi?pick=get&tp=549226

What is the appropriate K valuefor this to be a legitimate probability density function?

Im not exactly sure of the approach to this problem...

 

[Defennder]

Well all you need to do is to understand it means for some function to be considered a legitimate pdf. What criteria must it satisfy?