High School

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 want to find the polynomial quotient when dividing

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

by

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

We perform polynomial long division step by step.

1. Notice that the dividend is

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

and the divisor is

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

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

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

4. Subtract this product from the dividend:

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

Now, the new dividend is [tex]$5x^3 - 15$[/tex].

5. Next, divide the leading term of the new dividend, [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]$$
5 \cdot (x^3 - 3) = 5x^3 - 15.
$$[/tex]

7. Subtract this from the current dividend:

[tex]$$
\begin{aligned}
(5x^3 - 15) - (5x^3 - 15)
&= 5x^3 - 5x^3 - 15 + 15 \\
&= 0.
\end{aligned}
$$[/tex]

The remainder is [tex]$0$[/tex].

8. Since the division process ends with a remainder of [tex]$0$[/tex], the complete quotient is the sum of the terms we obtained:

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

Thus, the quotient of the division is

[tex]$$
\boxed{x+5}.
$$[/tex]