Long division is useful with the remainder and factor theorems, but long division can be time consuming. To divide a polynomial by a binomial and compute the remainder, we can also use synthetic division. We can only divide by a binomial whose leading coefficient is 1--thus, we must factor the leading coefficient out of the binomial and divide by the leading coefficient separately. Also, the binomial must have degree 1; we cannot use synthetic division to divide by a binomial like x² + 1. Here are the steps for dividing a polynomial by a binomial using synthetic division:

Write the polynomial in descending order, adding "zero terms" if an exponent term is skipped.
If the polynomial does not have a leading coefficient of 1, write the binomial as b(x - a) and divide the polynomial by b. Otherwise, leave the binomial as x - a.
Write the value of a, and write all the coefficients of the polynomial in a horizontal line to the left of a.
Draw a line below the coefficients, leaving room above the line.
Bring the first coefficient below the line.
Multiply the number below the line by a and write the result above the line below the next coefficient.
Subtract the result from the coefficient above it.
Repeat steps 6 and 7 until all the coefficients have been used.
If the polynomial has n terms, the first n - 1 numbers below the line are the coefficients of the resulting polynomial, and the last number is the remainder.