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 :

We need to divide the polynomial

[tex]$$
x^4+5x^3-3x-15
$$[/tex]

by

[tex]$$
x^3-3.
$$[/tex]

Let's perform the division step by step.

1. Write the dividend in full form (including terms with zero coefficients where necessary):

[tex]$$
x^4+5x^3+0x^2-3x-15.
$$[/tex]

2. Divide the leading term of the dividend, [tex]$x^4$[/tex], by the leading term of the divisor, [tex]$x^3$[/tex]:

[tex]$$
\frac{x^4}{x^3} = x.
$$[/tex]

So, the first term of the quotient is [tex]$x$[/tex].

3. Multiply the entire divisor by [tex]$x$[/tex]:

[tex]$$
x(x^3-3) = x^4-3x.
$$[/tex]

4. Subtract this product from the dividend:

[tex]$$
\begin{align*}
&\quad \left(x^4+5x^3-3x-15\right) - \left(x^4-3x\right) \\
&= x^4+5x^3-3x-15 - x^4+3x \\
&= 5x^3-15.
\end{align*}
$$[/tex]

5. Now, treat [tex]$5x^3-15$[/tex] as the new dividend. Divide its leading term, [tex]$5x^3$[/tex], by the leading term of the divisor, [tex]$x^3$[/tex]:

[tex]$$
\frac{5x^3}{x^3} = 5.
$$[/tex]

So, the next term of the quotient is [tex]$5$[/tex].

6. Multiply the divisor by [tex]$5$[/tex]:

[tex]$$
5(x^3-3) = 5x^3-15.
$$[/tex]

7. Subtract this from the current dividend:

[tex]$$
\begin{align*}
&\quad \left(5x^3-15\right) - \left(5x^3-15\right) \\
&= 0.
\end{align*}
$$[/tex]

Since the remainder is [tex]$0$[/tex], the division is exact and the quotient is

[tex]$$
x+5.
$$[/tex]

Thus, the quotient of the given division is [tex]$\boxed{x+5}$[/tex].