TWO OF CAMBRIDGE'S most serious problems are unemployment and a shortage of low and moderate-income housing. They have combined to make the city increasingly homogeneous, filled with well-paid professionals and a nationally famous educational elite.

A pair of recently proposed developments in East Cambridge would do nothing to stop that trend. In fact, they would help guarantee its continuation. For that reason, the Cambridge Redevelopment Authority's (CRA) revised plans for developing Kendall Square and a private developer's proposal for a 500-room hotel on Memorial Drive are unacceptable.

The CRA originally wanted to fill both the so-called Golden Triangle and the Quadrangle in Kendall Square with motels and garages, a retail shopping complex, office space and upper and middle-income apartments. After strong community opposition, the authority now proposes to go ahead only with its plans for the Golden Triangle, while trying to ease unemployment by finding light industry for the Quadrangle.

This is not good enough. Past experience with urban renewal in Boston and Cambridge induces skepticism about the CRA's promises, especially since it previously pleaded that it could not find any light industry for Kendall Square. The Golden Triangle and the Quadrangle must be considered as a single unit, and the CRA must try harder to both attract new manufacturing concerns to Cambridge and relocate light industry from predominantly residential sections of the city, thus opening up space for desperately needed low-income housing.

The proposed hotel, ranging in height from 6 to 15 stories and timed to capitalize on the tourist influx accompanying the Kennedy Library's completion, is not objectionable in and of itself, but because it would violate the proposed new Riverfront zone.

That new zone is important for two reasons. First, it would encourage additional moderate and low-income housing. Secondly, it would give the community more control over the future of the riverfront, guaranteeing neighborhood access to the Charles.

There are obviously compromises possible on both the Kendall Square and hotel issues. But the City Council, which will ultimately determine the fate of both projects, should remember that the advantage of increased tax revenue pales in comparison to the basic need of Cambridge working people for jobs and decent housing. Reducing the tax rate will do nothing for these people if they have left Cambridge because it gave exclusive attention to fancy frills and vested interests.