-べき(-beki) and its negative form | Japanese
-beki (in Japanese) is a particle attached to a dictionary form of a verb, and it means “should do” or “ought to do”.
hanasu → hanasubeki
taberu → taberubeki
suru → surubeki (or) subeki
1. Anata wa kare to hanasubeki da.（You should talk with him.）
2. Anata wa kare to hanasubeki desu.（You should talk with him.）
Negative form of -beki is “-bekidewa nai”
hanasubeki → hanasubeki dewanai
taberubeki → taberubeki dewanai
taberubeki → taberubeki dewa arimasen
3. Anata wa kare to hanasubeki dewanai.（You shouldn’t talk with him.）
4. Anata wa kare to hanasubeki dewanai desu.（You shouldn’t talk with him.）This is less used, but it is not wrong.
5. Anata wa kare to hanasubeki dewa arimasen.（You shouldn’t talk with him.）This is more sophisticated than No.4 sentence. I always use this one.
Some Japanese make mistakes in making its negative form and write “-naibeki”, but this is wrong.
