College

The quotient of [tex]$\left(x^4+5x^3-3x-15\right)$[/tex] and [tex]$\left(x^3-3\right)$[/tex] is a polynomial. What is the quotient?

A. [tex]$x^7+5x^6-6x^4-30x^3+9x+45$[/tex]
B. [tex]$x-5$[/tex]
C. [tex]$x+5$[/tex]
D. [tex]$x^7+5x^6+6x^4+30x^3+9x+45$[/tex]

Answer :

To find the quotient when dividing [tex]\(x^4 + 5x^3 - 3x - 15\)[/tex] by [tex]\(x^3 - 3\)[/tex], we will perform polynomial long division.

1. Set up the division: We'll divide the polynomial [tex]\(x^4 + 5x^3 - 3x - 15\)[/tex] by [tex]\(x^3 - 3\)[/tex].

2. Divide the leading terms:
- The leading term of the dividend (the polynomial we are dividing) is [tex]\(x^4\)[/tex].
- The leading term of the divisor is [tex]\(x^3\)[/tex].
- Divide these leading terms: [tex]\(\frac{x^4}{x^3} = x\)[/tex].
- This is the first term of our quotient.

3. Multiply and Subtract:
- Multiply the entire divisor [tex]\(x^3 - 3\)[/tex] by [tex]\(x\)[/tex], giving us [tex]\(x(x^3 - 3) = x^4 - 3x\)[/tex].
- Subtract this result from the original polynomial:
[tex]\[
(x^4 + 5x^3 - 3x - 15) - (x^4 - 3x) = 5x^3 + 0x^2 + 0x - 15
\][/tex]
- Simplifying gives us [tex]\(5x^3 - 0x^2 + 0x - 15\)[/tex].

4. Repeat the process:
- Divide the leading term of the new polynomial [tex]\(5x^3\)[/tex] by the leading term of the divisor [tex]\(x^3\)[/tex].
- [tex]\(\frac{5x^3}{x^3} = 5\)[/tex].
- Add this to the quotient so far, for a quotient of [tex]\(x + 5\)[/tex].

5. Multiply and Subtract:
- Multiply the entire divisor by this new term in the quotient: [tex]\(5(x^3 - 3) = 5x^3 - 15\)[/tex].
- Subtract:
[tex]\[
(5x^3 - 15) - (5x^3 - 15) = 0
\][/tex]
- There is no remainder.

Therefore, the quotient of [tex]\((x^4 + 5x^3 - 3x - 15)\)[/tex] divided by [tex]\((x^3 - 3)\)[/tex] is [tex]\(\boxed{x + 5}\)[/tex].