Polynomials are among the most common expressions in algebra. Each is just the sum of one or more powers of x, with each power multiplied by various numbers. In formal language, a polynomial in one variable, x, is the sum of terms axk where k is a nonnegative integer and a is a constant. Polynomials are to algebra about what integers (or whole numbers) are to arithmetic. They can be added, subtracted, multiplied, and factored. Division of one polynomial by another may leave a remainder.
There are various words that are used in conjunction with polynomials. The degree of a polynomial is the exponent of the highest power of x. Thus the degree of
2x3 + 5x2–x + 2
is 3. The leading coefficient is the coefficient of the highest power of x. Thus the leading coefficient of the above equation is 2. The constant term is the term that is the coefficent of x0 (= 1). Thus the constant term of the above equation is 2, whereas the constant term of x3 + 5x2 + x is 0.
The most general form for a polynomial in one variable is
anxn + an – 1xn – 1 + ... + a1x + a0
where an, an–1, ..., a1, a0 are real numbers. They can be classified according to degree. Thus a first-degree polynomial, a1x + a2, is linear; a second-degree polynomial a1x2 + a2x + a3 is quadratic; a third-degree polynomial, a3x3 + a2x2 + a1x + a0 is a cubic and so on.
An irreducible or prime polynomial is one that has no factors of lower degree than a constant. For example, 2x2 + 6 is an irreducible polynomial although 2 is a factor. Also x2 + 1 is irreducible even though it has the factors x + iandx–i that involve complex numbers. All polynomials are the product of irreducible polynomials, just as every integer is the product of prime numbers.
A polynomial in two variables, x and y, is the sum of terms, axkym where a is a real number and k and m are non-negative integers. For example,
x3y + 3x2y2 + 3xy–4x + 5y–12
is a polynomial in x and y. The degree of such a polynomial is the greatest of the degrees of its terms. Thus the degree of the above equation is 4–both from x3y(3 + 1←= 4) and from x2y2 (2 + 2 = 4).
Similar definitions apply to polynomials in 3, 4, 5 . . . variables, but the term “polynomial” without qualification usually refers to a polynomial in one variable.
A polynomial equation is of the form P = 0 where P is a polynomial. A polynomial function is one whose values are given by polynomial.
Bittinger, Marvin L., and David Ellenbogen. Intermediate Algebra: Concepts and Applications. 6th ed. Reading, MA: Addison-Wesley Publishing, 2001.
Larson, Ron. Precalculus. 5th ed. New York: Houghton Mifflin College, 2000.
Oak Road Systems. “Solving Polynomial Equations” <http://oakroadsystems.com/math/polysol.htm> [October 9, 2006).
Wolfram MathWorld. “Polynomial” <http://mathworld.wolfram.com/Polynomial.html> (accessed October 9, 2006).