There used to be a place called Centralia, Pennsylvania. The town incorporated in the 1860s and once had several thousand residents, largely coal workers. But the story of its demise begins a century later in 1962. That year, a trash burning fire was lit in the pit of the old abandoned coal mine outside of town. The fire moved down the mineshaft and ignited a vein of coal. It is still burning. For more than twenty years, people tried to extinguish the underground fire, but no matter what they did, it returned. There was little government action, and people had to abandon their homes as toxic gases engulfed the area and sinkholes developed. In 1983, engineers studying the fire concluded that it could burn for and could spread over nearly 4,000 acres.

In 1983, engineers studying the fire concluded that it could burn for 250 years and could spread over nearly 4,000 acres.

Explanation:

Centralia in Pennsylvania is a city that has a fire that will last for about 250 years and that has already consumed more than 15 square kilometers, having enough strength to spread over 4,000 acres. This fire did not happen by chance, but because of the creation of a landfill in an old coal mine. The problem is that before this landfill was created, the holes made by the coal mine were not closed, which caused many underground meters to be filled with garbage. One day, uncomfortable with the amount of garbage accumulated, the citizens and the city government decided to set fire to the whole landfill, which caused the centenary fire that will last for 250 years, according to experts.

A linear function has a constant rate of change, while a nonlinear function does not. For a table of values to be linear, the outputs must have a constant rate of change as the inputs increase by 1. On a graph, the function must be a straight line to be linear.