First, it’s crucial to define some basic terms. A polynomial is an expression that contains variables, coefficients, and constants. An example of a polynomial is 2x^3 + 4x^2 – 3x + 1. When dividing polynomials, we use the same process as we do with numbers, but instead of dividing by a single digit, we divide by a polynomial (which is made up of multiple terms). The result of polynomial division is usually a quotient (which is a polynomial expression) and a remainder (which is usually a smaller polynomial).
There are two main methods for dividing polynomials: long division and synthetic division. Long division is more versatile and can be used for any polynomial division problem. However, synthetic division is faster and is only used when dividing by a linear factor (i.e., a factor of the form ax + b).
To use long division, we set up the problem in a polynomial division format, with the divisor outside the long division bar and the dividend inside. We then divide the first term of the dividend by the first term of the divisor, which gives us the first term of the quotient. We then multiply the entire divisor by this term and subtract it from the dividend. The result is the new dividend, which we repeat the process with until no remainder is left.
Here is an example of long division:
Divide 3x^3 – 7x^2 – 2x + 5 by x – 2
First, we write out the problem in the polynomial division format:
2 | 3x^3 – 7x^2 – 2x + 5
Next, we divide the first term of the dividend by the first term of the divisor:
3x^3 / x = 3x^2
We then multiply the entire divisor by this term and subtract it from the dividend:
3x^2(x – 2) = 3x^3 – 6x^2
3x^3 – 7x^2 – 2x + 5 – 3x^3 + 6x^2 = -x^2 – 2x + 5
We repeat this process with the new dividend:
-2x / x = -2
-2(x – 2) = -2x + 4
-x^2 – 2x + 5 + (-2x + 4) = -x^2 – 4x + 9
Next, we divide the first term of this new dividend by the first term of the divisor:
-x^2 / x = -x
-x(x – 2) = -x^2 + 2x
-x^2 – 4x + 9 – (-x^2 + 2x) = -2x + 9
Finally, we divide the first term of this new dividend by the first term of the divisor:
-2x / x = -2
-2(x – 2) = -2x + 4
-2x + 9 – (-2x + 4) = 5
Therefore, the quotient is 3x^2 – 2x – 1 with a remainder of 5.
Synthetic division is a quicker method of dividing polynomials, but it can only be used when dividing by a linear factor. It works by skipping the variables and only focusing on their coefficients. Here is an example:
Divide x^3 + 3x^2 – 11x – 15 by (x + 2)
First, write out the coefficients of the dividend in descending order:
1 3 -11 -15
Next, take the opposite sign of the divisor’s constant (in this case, 2), and write it in the same row as the coefficients:
1 3 -11 -15
-2
Next, bring down the first coefficient:
1 3 -11 -15
-2 1
Next, multiply this new number by the divisor’s constant:
1 3 -11 -15
-2 1 -2
Next, add the product to the next coefficient:
1 3 -11 -15
-2 1 -2 -6
Repeat the process until all coefficients have been used:
1 3 -11 -15
-2 1 -2 -6
2 -2 6
The last number in the final row is the remainder (in this case, 6). The other coefficients (reading from left to right) are the terms of the quotient, which in this example is x^2 – 2x + 6.
In summary, dividing polynomials can be accomplished using either long division or synthetic division, depending on the factors involved. Success with these methods requires a solid understanding of polynomial terms and coefficients, as well as good arithmetic and algebraic skills. With regular practice, these techniques can be mastered and applied to more challenging polynomial division problems.