Equations are classified by the highest power (value of the exponent) of their unknowns. If this is one, the equation is of first degree. If this is two, the equation is of second degree, and so on. Equations of higher degree than one yield multiple possible values for their unknown quantities. These values are known as roots. The first-degree equation (the linear equation): 3x−9 = 0 (root: x = 3)
