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 Precambrian is usually considered to have three eons: the Hadean, the Archean and the Proterozoic. Some scientists recognize a fourth eon, which they call the Chaotian, which predates the others and is the time of the first formation of our solar system.he Proterozoic Eon is also called the Cryptozoic (age of hidden life). About 2.5 billion years ago, enough shield rock had formed to start recognizable geologic processes such as plate tectonics.