We can't use both. The answer is to use the one with the smaller absolute value: With this definition of. A slightly different formal definition of the limit is used when x goes to +/- infinity, since we really cannot subtract x from infinity or vice versa-remember, infinity is a concept, not a number. Formally, the expression. Means that.
During the long interval of the Precambrian Era (which includes approximately 90% of geologic time and includes three Eons: the Hadean, the Archean and the Proterozoic) the only inhabitants of the Earth were simple microscopic organisms, many of them comparable in size and complexity to modern-day bacteria.
The Archaea are a group of prokaryotic, single-celled microorganisms. In this they are similar to bacteria but these two groups evolved differently, and are classified as different domains in the three-domain system.Originally these organisms were named archaebacteria.rchaea were originally described in extreme environments, but have since been found in all habitats and may contribute up to 20% of total biomass. These cells are particularly common in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet.