Final answer:
Dealers can ensure vehicle history knowledge by obtaining a vehicle history report and conducting a comprehensive mechanical inspection to avoid selling "lemons" and maintain a trustworthy reputation.
Step-by-step explanation:
Dealers can take several steps to ensure they know the history of vehicles they buy or accept in trade. First, they can obtain a thorough vehicle history report from a reliable source, such as a national database, which would include information on past owners, accident history, repairs, and service records. Second, they can conduct a comprehensive mechanical inspection to identify any potential issues that might not be apparent through a vehicle history report. By taking these steps, dealers can help maintain a trustworthy reputation and offer long-term reliability to their customers, avoiding the pitfalls of selling vehicles that could be considered "lemons" and thereby risking their business's credibility and long-term profitability.