High School

Divide using long division:

[tex]\[
\frac{3x^5 - 22x^4 + 13x^3 - 39x^2 + 14x + 6}{x^3 + 6x^2 - 3x + 5}
\][/tex]

(Show work)

Answer :

We wish to divide

[tex]$$
3x^5 - 22x^4 + 13x^3 + 39x^2 + 14x + 6
$$[/tex]

by

[tex]$$
x^3 + 6x^2 - 3x + 5.
$$[/tex]

We will do so by long division.

–––––––––––––––––––––––
Step 1. Determine the first term of the quotient

Divide the leading term of the numerator by the leading term of the divisor:

[tex]$$
\frac{3x^5}{x^3} = 3x^2.
$$[/tex]

Multiply the entire divisor by [tex]$3x^2$[/tex]:

[tex]$$
3x^2 \cdot \left(x^3 + 6x^2 - 3x + 5\right) = 3x^5 + 18x^4 - 9x^3 + 15x^2.
$$[/tex]

Subtract this product from the original numerator:

[tex]\[
\begin{array}{rcl}
\text{Numerator} &=& 3x^5 - 22x^4 + 13x^3 + 39x^2 + 14x + 6,\\[1mm]
\text{Product} &=& 3x^5 + 18x^4 - 9x^3 + 15x^2.
\end{array}
\][/tex]

Performing the subtraction:

[tex]\[
\begin{aligned}
3x^5 - 3x^5 &= 0,\\[1mm]
-22x^4 - 18x^4 &= -40x^4,\\[1mm]
13x^3 - (-9x^3) &= 22x^3,\\[1mm]
39x^2 - 15x^2 &= 24x^2,\\[1mm]
\text{Bring down } 14x + 6.
\end{aligned}
\][/tex]

So, the new remainder is

[tex]$$
-40x^4 + 22x^3 + 24x^2 + 14x + 6.
$$[/tex]

–––––––––––––––––––––––
Step 2. Find the next term of the quotient

Divide the new remainder’s leading term by the divisor’s leading term:

[tex]$$
\frac{-40x^4}{x^3} = -40x.
$$[/tex]

Multiply the divisor by [tex]$-40x$[/tex]:

[tex]$$
-40x \cdot \left(x^3 + 6x^2 - 3x + 5\right) = -40x^4 - 240x^3 + 120x^2 - 200x.
$$[/tex]

Subtract this from the previous remainder:

[tex]\[
\begin{array}{rcl}
\text{Previous remainder} &=& -40x^4 + 22x^3 + 24x^2 + 14x + 6,\\[1mm]
\text{Product} &=& -40x^4 - 240x^3 + 120x^2 - 200x.
\end{array}
\][/tex]

Subtracting gives:

[tex]\[
\begin{aligned}
-40x^4 - (-40x^4) &= 0,\\[1mm]
22x^3 - (-240x^3) &= 262x^3,\\[1mm]
24x^2 - 120x^2 &= -96x^2,\\[1mm]
14x - (-200x) &= 214x,\\[1mm]
\text{Bring down } + 6.
\end{aligned}
\][/tex]

Now the remainder becomes

[tex]$$
262x^3 - 96x^2 + 214x + 6.
$$[/tex]

–––––––––––––––––––––––
Step 3. Find the next term of the quotient

Divide the leading term of the current remainder by [tex]$x^3$[/tex]:

[tex]$$
\frac{262x^3}{x^3} = 262.
$$[/tex]

Multiply the divisor by [tex]$262$[/tex]:

[tex]$$
262 \cdot \left(x^3 + 6x^2 - 3x + 5\right) = 262x^3 + 1572x^2 - 786x + 1310.
$$[/tex]

Subtract this product from the current remainder:

[tex]\[
\begin{array}{rcl}
\text{Current remainder} &=& 262x^3 - 96x^2 + 214x + 6,\\[1mm]
\text{Product} &=& 262x^3 + 1572x^2 - 786x + 1310.
\end{array}
\][/tex]

Subtracting term‐by‐term:

[tex]\[
\begin{aligned}
262x^3 - 262x^3 &= 0,\\[1mm]
-96x^2 - 1572x^2 &= -1668x^2,\\[1mm]
214x - (-786x) &= 1000x,\\[1mm]
6 - 1310 &= -1304.
\end{aligned}
\][/tex]

So, the final remainder is

[tex]$$
-1668x^2 + 1000x - 1304.
$$[/tex]

–––––––––––––––––––––––
Final Result

The quotient obtained is the sum of the individual quotient terms:

[tex]$$
\text{Quotient} = 3x^2 - 40x + 262,
$$[/tex]

and the remainder is

[tex]$$
-1668x^2 + 1000x - 1304.
$$[/tex]

Thus, the division can be written as:

[tex]$$
\frac{3x^5 - 22x^4 + 13x^3 + 39x^2 + 14x + 6}{x^3 + 6x^2 - 3x + 5} = 3x^2 - 40x + 262 + \frac{-1668x^2 + 1000x - 1304}{x^3 + 6x^2 - 3x + 5}.
$$[/tex]

This is the complete step-by-step solution of the long division.