High School

The quotient of [tex]x^4+5x^3-3x-15[/tex] and [tex]x^3-3[/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 of the polynomial [tex]\((x^4 + 5x^3 - 3x - 15)\)[/tex] when divided by [tex]\((x^3 - 3)\)[/tex], we use polynomial long division.

1. Write the Polynomials:
- Dividend (numerator): [tex]\( x^4 + 5x^3 + 0x^2 - 3x - 15 \)[/tex]
- Divisor: [tex]\( x^3 - 0x^2 - 0x - 3 \)[/tex]

2. Perform the Division:
- First Term: Divide the leading term of the dividend [tex]\(x^4\)[/tex] by the leading term of the divisor [tex]\(x^3\)[/tex] to get [tex]\(x\)[/tex].
Multiply the entire divisor by [tex]\(x\)[/tex] to get [tex]\(x^4 - 3x\)[/tex].
- Subtract: Subtract [tex]\(x^4 - 3x\)[/tex] from the original dividend:
[tex]\[
(x^4 + 5x^3 + 0x^2 - 3x - 15) - (x^4 - 3x) = 5x^3 + 0x^2 + 0x - 15
\][/tex]

- Second Term: Divide the leading term [tex]\(5x^3\)[/tex] by the leading term of the divisor [tex]\(x^3\)[/tex] to get [tex]\(5\)[/tex].
Multiply the entire divisor by [tex]\(5\)[/tex] to get [tex]\(5x^3 - 15\)[/tex].
- Subtract Again: Subtract:
[tex]\[
(5x^3 + 0x^2 + 0x - 15) - (5x^3 - 15) = 0x^3 + 0x^2 + 0x + 0
\][/tex]

3. Identify the Quotient and the Remainder:
- The Division stops here because the degree of the remaining polynomial is less than the degree of the divisor.
- The quotient is [tex]\(x + 5\)[/tex].
- The remainder is 0.

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