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.
1 Dinosaurs were reptiles that lived on Earth from about 230 million years ago to about 65 million years ago. 2  b. 3  Dinosaurs lived during a period of Earthâs history called the Mesozoic (âmiddle lifeâ) Era. 4  They lived during all three periods of this era: the Triassic, Jurassic, and Cretaceous. a.