Synthetic Division Calculator
Welcome to our synthetic division calculator! It helps you perform the synthetic division of polynomials while showing all the intermediate steps at the same time!
Have you ever wondered what synthetic division is? Do you need to learn how to do synthetic division? We teach you everything you need to know about dividing polynomials using synthetic division, provide examples of synthetic division with steps, and explain how to use synthetic division to find zeros.
As a bonus, we show you how to deal with nonmonic and quadratic divisors!
Synthetic division of polynomials – definition
Before we can explain how to divide polynomials using synthetic division, let's refresh a few basic notions:
What are polynomials?
A polynomial is an expression involving a sum of nonnegative integer powers of at least one variable, each multiplied by real (or complex) numbers, which we call coefficients.
A polynomial in one variable, x (a univariate polynomial), is given by
a_{n}x^{n} + a_{n1}x^{n1} + ... + a_{1}x + a_{0},
where a_{n}, a_{n1},..., a_{1}, a_{0} are the coefficients. We call the individual terms of the form a_{k}x^{k} monomials. The leading coefficient of this polynomial is the coefficient of the term with the highest power of x, i.e., the coefficient a_{n}, provided that a_{n} ≠ 0. We say a polynomial is monic if its leading coefficient is equal to one: a_{n} = 1.
The degree of a polynomial is the value of the greatest exponent present in the polynomial with a nonzero coefficient. The polynomial written above has degree n, provided that a_{n} ≠ 0. Constant nonnull polynomials have degree zero. A null polynomial has its degree left undefined or, sometimes, defined as ∞ (negative infinity). We usually denote the degree of a polynomial with deg.
Polynomial division
The division of polynomials is analogous to dividing integers with remainder, which you've most probably encountered in arithmetic. Let P(x) and D(x) be two polynomials. If D(x) is nonzero, then there exist two polynomials, Q(x) and R(x), which satisfy:
P(x) = D(x) ⋅ Q(x) + R(x)
and deg(R) < deg(D). Moreover, Q(x) and R(x) are unique, i.e., there's no other pair of polynomials that satisfy these two conditions.
The terms we use in polynomial division are analogous to those in arithmetic: P(x) is called the dividend, D(x) is the divisor, Q(x) is a quotient, and R(x) is the remainder.
Note that:
 R(x) = 0 if, and only if, P(x) has D(x) as a factor; and
 If deg(P) < deg(Q), then D(x) = 0 and P(x) = R(x).
The standard way of calculating the quotient and remainder, given a dividend and divisor, is via the algorithm called the polynomial long division.
What is the synthetic division of polynomials?
Synthetic division is a shortcut way of dividing polynomials. It gives the same results as the polynomial long division but is much faster as it involves only the coefficients of the dividend and divisor, on which we perform basic arithmetic operations. As a result, we obtain the coefficients of the quotient and the remainder.
At a first look, you may find synthetic division a bit complicated, but rest assured: once you get the hang of it, you'll never look back!
Synthetic division is most commonly used when dividing by linear monic polynomials x  b. Dividing by such polynomials is very important in the context of finding zeroes and factoring polynomials: to verify whether b is a root of a polynomial, we can synthetically divide this polynomial by x  b and check if the remainder is equal to zero. For details, check out the section below, where we discuss how to use synthetic division to find the zeros of a polynomial.
Keep in mind that synthetic division works for any polynomial divisors: for nonmonic polynomials as well as for polynomials of degrees higher than one. However, it becomes more and more complicated as the degree of the divisor grows. In this article, we'll discuss in detail some synthetic division examples of nonmonic linear polynomials b_{1}x + b_{0} and quadratic polynomials c_{2}x^{2} + c_{1}x + c_{0}.
So, let's dive in and learn how to divide polynomials using synthetic division!
How to do synthetic division? Linear monic divisors
This section describes how to do synthetic division if the divisor is of the form x  b. For examples of synthetic division with divisors of a more complicated form, see the subsequent sections.
💡 It was Paolo Ruffini who described such division back in 1804. That's why you can sometimes encounter the term Ruffini's rule instead of synthetic division.
Since synthetic division is best explained with an example, we'll divide 3x^{3}  8x  9 by x  2. Let's discuss in detail how to do synthetic division.

Set up the synthetic division table. It consists of three rows:

In the first row, put the coefficients of the dividend in descending powers of x, inserting
0
's for any missing powers. In our example, the x^{2} term is missing, so we add0
between3
and8
, i.e., between the coefficients of x^{3} and x. 
In the second row and one column to the left, write
b
from the divisor x  b. In our case,b = 2
. It is common to write the multiplication sign in front ofb
and to separate it from the coefficients with a vertical bar. This is because the role this number plays in synthetic division is different than that of the coefficients. 
We leave the third row blank  we'll fill it up as we go.

 Drop the leading coefficient of the dividend to the bottom row.
 Multiply this dropped number by the number
b
on the left (in our case, it's multiplication by2
). Place the result under the next coefficient of the dividend.
 Sum the numbers in the column we created in the previous step. Write the result in the bottom row.
 Repeat Steps 3. and 4. until the table is full. We'll show you how to do it:
 Multiply the
6
we obtained above byb = 2
and write the result in the next column.
 Add
8
and12
together and write the sum in the last row.
 Multiply the
4
we obtained above byb = 2
and write the result in the next column.
 Add
9
and8
together and place the result in the last row.
 OK, the table is full. The result of the polynomial division we're looking for is here: the coefficients of the quotient and the remainder of this division can be found in the last row of our table!
The last value on the right is the remainder, and all the other values are the consecutive coefficients of the quotient, starting from the leading coefficient (working left to right):
 Coefficients of the quotient: 3, 6, 4
 Quotient: 3x^{2} + 6x + 4
 Remainder: 1
Synthetic division for nonmonic linear divisors
We will now see how to perform a synthetic division if the divisor is in the form b_{1}x + b_{0}, i.e., linear but not necessarily monic. As an example, let's divide 4x^{3} + 2x^{2}  2x + 1 by 2x + 1.
 Set up the division table. It's very similar to that for monic divisors, but the main difference is the presence of the fourth row, where we place the leading coefficient b_{1} of the divisor preceded by the division sign :. Also, be careful with the signs: we write b_{0} at the beginning of the second row!
 Drop the leading coefficient of the dividend to the third row.
 Divide the number you've just placed in the third row by
2
and put the result in the last row.
 Multiply this dropped number by the number on the left. Place the result under the next coefficient of the dividend.
 Sum the numbers in the column we created in the previous step. Write the result in the third row.

Repeat Steps 3. & 4. & 5. until the table is (almost) full – you don't need to perform the last division.
In our example, we obtain the following table (check it yourself!):
 This time, to find the coefficients of the quotient and the remainder, you need to take a look at the last two rows of our table.
The last value of the penultimate row is the remainder of the division, and the values in the last row are the coefficients of the quotient: working left to right, the first number is the leading coefficient of the quotient, and the last one is the constant.
 Coefficients of the quotient: 2, 0, 1
 Quotient: 2x^{2}  1
 Remainder: 2