Final answer:
The sons sold Joseph to traders and presented their father with Joseph's bloody coat, making him think Joseph was dead.
Step-by-step explanation:
The sons did several things to make their father think Joseph was dead. They first sold Joseph to a group of traders, who then took him to Egypt. To convince their father, they dipped Joseph's multicolored coat in animal blood and presented it to him, making him believe that Joseph had been killed by a wild animal.