Solve App problem

[kruki]

Thank you informach for quick replay but I just discover some weird results.
I checked "V" and "P" as variables and changed the values of "N" from 1 to 10.
If I put number 2,4 and 8 for "N" "Cannot find solution" error appears. Numbers 1,3,5,6,7,9,10 solve equation but variable "P" gives strange results (for example if I put for "N" 1000 "P" is 15 instead of 1562,5).
Thanks