What were the five planets that
the ancient Greeks found?

Six planets have been known to humanity as long as anybody has been interested enough to look at the sky at night.  That includes the ancient Chinese, Babylonians, Persians, Assyrians, Mongols, Hebrews, Egyptians, Greeks, Romans, etc.

They are the six that you can see with only your eyes and no telescope:

-- Mercury

-- Venus

-- Earth

-- Mars

-- Jupiter

-- Saturn

reflecting point a across the origin negates both of its coordinates.

b = (5, -4)