High School

What is the remainder when [tex]3x^3 - 2x^2 + 4x - 3[/tex] is divided by [tex]x^2 + 3x + 3[/tex]?

A. 30
B. [tex]3x - 11[/tex]
C. [tex]28x - 36[/tex]
D. [tex]28x + 30[/tex]

Answer :

To find the remainder when dividing [tex]\(3x^3 - 2x^2 + 4x - 3\)[/tex] by [tex]\(x^2 + 3x + 3\)[/tex], we need to use polynomial long division. Let's work through the steps:

1. Setup the Division: We will divide [tex]\(3x^3 - 2x^2 + 4x - 3\)[/tex] by [tex]\(x^2 + 3x + 3\)[/tex].

2. Divide the Leading Terms: Divide the leading term of the dividend, [tex]\(3x^3\)[/tex], by the leading term of the divisor, [tex]\(x^2\)[/tex]. This gives [tex]\(3x\)[/tex].

3. Multiply and Subtract: Multiply [tex]\(3x\)[/tex] by the entire divisor [tex]\((x^2 + 3x + 3)\)[/tex], which gives [tex]\(3x^3 + 9x^2 + 9x\)[/tex]. Now subtract this from the original polynomial:

[tex]\[
(3x^3 - 2x^2 + 4x - 3) - (3x^3 + 9x^2 + 9x) = -11x^2 - 5x - 3
\][/tex]

4. Repeat the Process: Now divide the new leading term [tex]\(-11x^2\)[/tex] by the leading term of the divisor, [tex]\(x^2\)[/tex], which gives [tex]\(-11\)[/tex].

5. Multiply and Subtract Again: Multiply [tex]\(-11\)[/tex] by the entire divisor, resulting in [tex]\(-11x^2 - 33x - 33\)[/tex]. Subtract this from [tex]\(-11x^2 - 5x - 3\)[/tex]:

[tex]\[
(-11x^2 - 5x - 3) - (-11x^2 - 33x - 33) = 28x + 30
\][/tex]

6. Identify the Remainder: The result of [tex]\(28x + 30\)[/tex] is the remainder, because it has a lower degree than the divisor [tex]\(x^2 + 3x + 3\)[/tex].

So, the remainder when [tex]\(3x^3 - 2x^2 + 4x - 3\)[/tex] is divided by [tex]\(x^2 + 3x + 3\)[/tex] is [tex]\(28x + 30\)[/tex].

Thus, the correct answer is [tex]\(\boxed{28x + 30}\)[/tex].