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.
Ice, Megafauna and Hominids. The Quaternary Period began with an ice age about 1.8 million years ago. It is often called the Age of Humans. It continues up to the present time and is the period that we live in.It is divided into two epochs 1  : The Pleistocene Epoch - 1.8 million to 11,000 years ago. 2  The Holocene Epoch - 11,000 years ago to present.ce, Megafauna and Hominids. The Quaternary Period began with an ice age about 1.8 million years ago. It is often called the Age of Humans. It continues up to the present time and is the period that we live in.