LinkedIn Corp. shares fell after the company attributed a bump in its annual revenue forecast to its acquisition of the education website Lynda.com, raising concerns that growth is slowing in its main business.

LinkedIn said full-year sales would be about $2.94 billion, beating the $2.91 billion average of analysts’ estimates compiled by Bloomberg. As part of the forecast, the company more than doubled expectations for revenue from the Lynda.com acquisition to $90 million for the year, raising questions about whether the professional-networking website’s core business was expected to slow.

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The company acquired Lynda.com for $1.5 billion while it also reorganized its sales force and changed advertising methods — expensive moves that may take time to produce benefits. The Lynda.com purchase and LinkedIn’s efforts to promote news content are intended to make the website valuable to people even when they aren’t looking for jobs.

“I don’t think investors have a clear sense of the contributions from Lynda and what that means to the core growth,” said Paul Sweeney, an analyst at Bloomberg Intelligence. “Investors I spoke with voiced concern about a meaningful guidance increase the quarter after a surprising reduction.”

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The company had cut its annual revenue forecast on April 30, citing the effect of the strong U.S. dollar on international sales and slower growth.

Share Fluctuations

LinkedIn initially rose as much as 15 percent in extended trading after the earnings were released, only to erase those gains and fall as low as 9 percent to $207 during the company’s conference call with investors. Earlier, LinkedIn fell 2.1 percent to $227.15 at the close in New York. The stock has declined 1.1 percent this year.

The company’s second-quarter earnings, excluding some items, were 55 cents a share, compared with the estimate of 30 cents.

Second-quarter sales increased 33 percent to $711.7 million, while analysts’ estimated $679.9 million. LinkedIn’s loss widened to $67.7 million, or 53 cents, from $1.03 million, or 1 cent, a year earlier, the Mountain View, California-based company said.

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LinkedIn’s Talent Solutions business was its fastest-growing segment in the quarter, gaining 38 percent to $433 million after the sales force shake-up.

The jobs site, which reported 380 million users, said those people spent 60 percent more time on LinkedIn than they did a year earlier. The company reduced the amount of e-mails it sends out by 40 percent to reduce complaints and improve the quality of the experience. The company said its China-based site now has more than 10 million members.

LinkedIn is “navigating through some temporary hiccups that they should be able to put behind them,” said James Cakmak, an analyst at Monness Crespi Hardt & Co. Still, “it’s one of the most compelling investment opportunities in the Internet space right now.”

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