I Have a formula but WA#4 ????

I have a formula but I have WA#4 ? Sqrt - is a only one function, that I use. All other members of formula use +,-,*,/ ? What's going on ?

Help, please!

And a question more!

They wrote that we need 4 symbols after comma, but in the sample - 6. I sent my program with both variants and got WA#4? How it can be?

Sorry for bad English.