Given only three points, if they don't lie on a line, it is quite hard to guess what the whole graph should be like... It is like you would be given the color of three pixels on a picture: if the three pixels are black, a natural guess (but not necessarily a good one) would be that the whole picture is black, but if the colors are different, we have no clue and there's not much we can guess. I can give you one thousand formulas of graphs that go through the three points, but this would be pointless.
Perhaps it could help if you tell us what these points correspond to. Or give a few more points.