Equations and their solutions

An equality containing an unknown number denoted by a letter is called an equation, for example 6x + 2000 = 8000. The expressions to the left and to the right of the equals sign are the left and right sides of the equation, and each term in them is a term of the equation. A value of the unknown that turns the equation into a true equality is a root of the equation; we can check a root by substituting it. An equation may have one root, two roots or several, infinitely many roots, or no roots at all. To solve an equation means to find all its roots or to show that there are none. An equation of the form ax = b is called a linear equation (a and b are given numbers).