Mastering Technical Mathematics, Third Edition, 3rd Edition

10	Quadratic Equations

Simultaneous equations come from problems that have two or more answers “at the same time.” Quadratic equations can represent another kind of problem where different answers exist, not “at the same time” but as alternatives. Quadratic equations are also called second-order equations because they involve raising a variable to the second power (squaring it).

A QUADRATIC EXAMPLE

Suppose you have 80 feet of fencing available to make a rectangular enclosure such as a pen for your dog. How much area will the fence enclose? That, of course, depends on the width and the length of the rectangle, both of which can vary. If the rectangle is W feet wide by L feet long, then 2W + 2L = 80. Dividing through by 2 tells you that ...