Hamlet- Act 1 Scene 5

What does the ghost tell Hamlet? that King Hamlet was murdered by Claudius and to avenge his murder
How does the Ghost want Hamlet to treat Claudius? Gertrude? He wants him to kill Claudius but to spare his mother Gertrude.
What does Hamlet make Horatio and Marcellus swear? Why? He makes them swear that they will keep secret the incident with the ghost; He is plotting revenge against Claudius.