Consumer products giant Procter & Gamble Co. slipped after it lowered its fourth-quarter earnings and revenue forecasts, the latest company to warn about slowing global economic growth. P&G, which makes an array of everyday goods ranging from Tide detergent to Gillette razors, said it is cutting the forecast because of unfavorable foreign-exchange rates, continued slow growth in developed markets, and a slowdown in China. Many US companies have looked to emerging markets as economic growth in North America and Europe has slowed. But P&G’s and others’ warnings show that expanding abroad is a complicated task, even for large companies.