A quadratic equation is an equation that can be written in the form ax2 + bx + c = 0, where a, b, and c are any real numbers with a ≠ 0. Any number, x, that satisfies the equation is called a solution or a root of the equation.
Although some quadratic equations can be solved by other, sometimes easier, methods—including factoring—that will be discussed later, every quadratic equation can be solved by using the quadratic formula given in KEY FACT E1.
Key Fact E1