Google has reportedly conferred with at least two private equity firms about helping them finance a deal to buy Yahoo, although they have not yet put together a formal proposal. Antitrust regulators would monitor such a deal, because both of the companies hold a large share of the Internet search business. Yahoo’s stock price has recently gone up because investors are betting that the company will be sold soon. Shares are up 45 percent since August. In 2008, Microsoft offered to buy Yahoo for $47.5 billion.