What was going on when I was born?

President Reagan's proposal for a Federal takeover of Medicaid costs in exchange for the states' takeover of food stamps and payment to poor families with dependent children could have short-range benefits to New York, Connecticut and New Jersey, officials of the three states said today. However, they agreed that the states could be more financially pressed than they are now by the longer-range proposal to turn a variety of Federal programs back to the states. The nation's governors divided in unusually partisan ranks in assessing the President's proposals, with Democratic criticism somewhat more solid than Republican support. (Page B8.) Amount at Issue Of immediate concern to New York State, New Jersey and Connecticut was how much of the Medicaid program -which is generous in the tristate area compared with elsewhere in the country - would be picked up by the Federal Government.

International Talks on Palestinian self-rule moved into a new phase as the United offered some new formulas to Israeli leaders. Secretary of State Alexander M. Haig Jr. met with Prime Minister Menachem Begin of Israel in an effort to overcome the Israeli differences with Egypt, which have for more than 2 years blocked an accord. (Page1,Column 2.) Peasants in El Salvador are being trained by the Farabundi MartiLiberation Front to become guerrilla fighters. In a school run by the front, Marxist political principles are an integral part of the curriculum for the peasant soldiers, few of whom are more than 24 or 25 years old. (A1:2-4.)

''I liked it better when the actors kept their clothes on.'' - Ronald Reagan. (B8:5.)

An article yesterday about a Young Playwrights Festival incorrectly iden- tified the president of the Dramatists Guild. He is Peter Stone.

The failure of a crucial valve during the nuclear accident in Ontario, N.Y., Monday allowed a steam bubble to form in the reactor vessel, officials of Rochester Gas and Electric said yesterday. They said the bubble briefly raised the possibility that the nuclear core might be uncovered and cause the kind of damage that occurred at the Three Mile Island plant in March 1979. The existence of the bubble was disclosed when Rochester Gas, which operates the Robert E. Ginna plant in Ontario, released a chronology of the accident. Since Tuesday, the day after the accident, the plant has been in a stable, ''cold shutdown'' condition.

The Bronx District Attorney said yesterday that a surgeon at Montefiore Hospital was a suspect in a near-fatal hammer attack New Year's Eve on a woman who worked with him. Mario Merola, the District Attorney, also said that the suspect, Dr. Richard G. Rosen, after learning that the assistant, Clara Vanderbilt, would survive the assault, made statements on two audio cassette recordings and then tried to commit suicide. Mrs. Vanderbilt, who is 40 years old, was the director of the physicians assistant program at the Bronx hospital, where Dr. Rosen is vice chairman of the department of surgery. She was struck from behind on the head seven to 10 times with a hammer while she was in Dr. Rosen's office at the hospital on the evening of Dec. 31. Merola Seeks 2 Tapes The disclosure that the 51-year-old Dr. Rosen was under investigation and that he had tried to kill himself was made yesterday when Mr. Merola's office filed a motion in Criminal Court in the Bronx. It moved to obtain the two tape cassettes, which are in the possession of the surgeon's lawyer, Jonathan Rosner.

The RCA Corporation announced yesterday that its earnings for last year's fourth quarter fell 26.9 percent, while profits for the full year plummeted 82.9 percent - the second-largest annual decline in the company's 63-year history. The drop-off in profits was attributed to a variety of operating and financial problems afflicting almost every major division of the giant electronics and communications conglomerate. These included poor ratings for its NBC subsidiary, weak earnings from its Hertz Corporation rent-a-car business, slow sales of its Selectavision videodisk player, write-offs of several money-losing assets and rising interest costs on the multibillion-dollar debt it accumulated trying to diversify. ''The company has really come unglued in the last year,'' said George Smith, communications analyst for Provident National Bank. ''Almost every part of RCA is having problems. The big question now is whether they will have to reduce the dividend.''

In his first State of the Union Message, President Reagan conceded that the recession had wrecked his Administration's early economic forecasts. But he once again asserted that his program, based first and foremost on supply-side economics, would work. Economists still have varied reactions to the plan. But they now agree, perhaps more than ever before, on the one problem that Mr. Reagan should focus on. Last year some felt it was more important to worry about inflation. Others were more concerned about spurring the economy.

East Harlem has experienced a dramatic increase in the number of people who say they have inadequate food supplies for themselves and their families, a study by a coalition of voluntary agencies suggests. The agencies report a fivefold increase in one year in the number of people who sought food assistance from them. The coalition believes its survey probably reflects a pattern of similar conditions throughout East Harlem. The study, which was made before people living in the area began to feel the impact of Federal budget cuts, is still being analyzed to determine the causes for the sharp rise. Interviews with members of the coalition, known as the East Harlem Interfaith Welfare Committee, and with some people who received emergency food from the agencies in the group indicated that one important reason for the increase in requests for food was the crippling effect that inflation had on welfare and other entitlement benefits.

The Treasury yesterday announced a $10 billion financing package for sale next week - a record borrowing and a vivid reminder to the credit markets that the Federal budget is deeply in deficit. Prices of outstanding Treasury notes and bonds declined modestly after the announcement and yields rose, mainly because the financing was larger than the $9.5 billion that had been widely forecast by securities dealers. Among outstanding Treasury issues, three- and ten-year notes were offered late yesterday with yields of 14.66 percent and 14.53 percent, respectively. The outstanding 14 percent bonds due in 2011 were offered at 98 1/4 to yield 14.25 percent.

The United States opened a new phase today in the drawn-out negotiations on Palestinian self-rule by offering Israel some new formulas for resolving differences with Egypt. Secretary of State Alexander M. Haig Jr., in his second trip to the area in two weeks, spent seven hours - two of them alone with Prime Minister Menachem Begin - laying out the latest ideas. Mr. Haig, who arrived this afternoon from Geneva after a meeting with Foreign Minister Andrei A. Gromyko of the Soviet Union, will fly to Cairo tomorrow to present the proposals to President Hosni Mubarak of Egypt. The proposals have not been made public.

The Treasury announced a $10 billion financing package for sale next week, higher than securities dealers had expected. They said they expected strong demand despite high interest rates. Prices of outstanding Treasury notes and bonds declined modestly after the announcement. (Page D1.) The stock market edged higher after showing modest declines in the past three sessions. The Dow Jones industrial average rose 1.15 points, to 842.66. (D8.) The dollar was mixed in foreign currency trading. Gold rose $8.25 an ounce, to $383.25, in New York. (D13.) Soybean futures rallied. (D13.)