Precalculus Examples

$6 x^{2} + x + \frac{12}{3 x^{2} - 5 x - 2}$

Step 1

Find where the expression $6 x^{2} + x + \frac{12}{3 x^{2} - 5 x - 2}$ is undefined.

$x = - \frac{1}{3}, x = 2$

Step 2

Since $6 x^{2} + x + \frac{12}{3 x^{2} - 5 x - 2}$ $\to$ $\infty$ as $x$ $\to$ $- \frac{1}{3}$ from the left and $6 x^{2} + x + \frac{12}{3 x^{2} - 5 x - 2}$ $\to$ $- \infty$ as $x$ $\to$ $- \frac{1}{3}$ from the right, then $x = - \frac{1}{3}$ is a vertical asymptote.

$x = - \frac{1}{3}$

Step 3

Since $6 x^{2} + x + \frac{12}{3 x^{2} - 5 x - 2}$ $\to$ $- \infty$ as $x$ $\to$ $2$ from the left and $6 x^{2} + x + \frac{12}{3 x^{2} - 5 x - 2}$ $\to$ $\infty$ as $x$ $\to$ $2$ from the right, then $x = 2$ is a vertical asymptote.

$x = 2$

Step 4

List all of the vertical asymptotes:

$x = - \frac{1}{3}, 2$

Step 5

Consider the rational function $R (x) = \frac{a x^{n}}{b x^{m}}$ where $n$ is the degree of the numerator and $m$ is the degree of the denominator.

1. If $n < m$ , then the x-axis, $y = 0$ , is the horizontal asymptote.

2. If $n = m$ , then the horizontal asymptote is the line $y = \frac{a}{b}$ .

3. If $n > m$ , then there is no horizontal asymptote (there is an oblique asymptote).

Step 6

Find $n$ and $m$ .

$n = 4$

$m = 2$

Step 7

Since $n > m$ , there is no horizontal asymptote.

No Horizontal Asymptotes

Step 8

Find the oblique asymptote using polynomial division.

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Step 8.1

Combine.

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Step 8.1.1

Find the common denominator.

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Step 8.1.1.1

Write $6 x^{2}$ as a fraction with denominator $1$ .

$\frac{6 x^{2}}{1} + x + \frac{12}{3 x^{2} - 5 x - 2}$

Step 8.1.1.2

Multiply $\frac{6 x^{2}}{1}$ by $\frac{3 x^{2} - 5 x - 2}{3 x^{2} - 5 x - 2}$ .

$\frac{6 x^{2}}{1} \cdot \frac{3 x^{2} - 5 x - 2}{3 x^{2} - 5 x - 2} + x + \frac{12}{3 x^{2} - 5 x - 2}$

Step 8.1.1.3

Multiply $\frac{6 x^{2}}{1}$ by $\frac{3 x^{2} - 5 x - 2}{3 x^{2} - 5 x - 2}$ .

$\frac{6 x^{2} (3 x^{2} - 5 x - 2)}{3 x^{2} - 5 x - 2} + x + \frac{12}{3 x^{2} - 5 x - 2}$

Step 8.1.1.4

Write $x$ as a fraction with denominator $1$ .

$\frac{6 x^{2} (3 x^{2} - 5 x - 2)}{3 x^{2} - 5 x - 2} + \frac{x}{1} + \frac{12}{3 x^{2} - 5 x - 2}$

Step 8.1.1.5

Multiply $\frac{x}{1}$ by $\frac{3 x^{2} - 5 x - 2}{3 x^{2} - 5 x - 2}$ .

$\frac{6 x^{2} (3 x^{2} - 5 x - 2)}{3 x^{2} - 5 x - 2} + \frac{x}{1} \cdot \frac{3 x^{2} - 5 x - 2}{3 x^{2} - 5 x - 2} + \frac{12}{3 x^{2} - 5 x - 2}$

Step 8.1.1.6

Multiply $\frac{x}{1}$ by $\frac{3 x^{2} - 5 x - 2}{3 x^{2} - 5 x - 2}$ .

$\frac{6 x^{2} (3 x^{2} - 5 x - 2)}{3 x^{2} - 5 x - 2} + \frac{x (3 x^{2} - 5 x - 2)}{3 x^{2} - 5 x - 2} + \frac{12}{3 x^{2} - 5 x - 2}$

Step 8.1.2

Combine the numerators over the common denominator.

$\frac{6 x^{2} (3 x^{2} - 5 x - 2) + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3

Simplify each term.

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Step 8.1.3.1

Apply the distributive property.

$\frac{6 x^{2} (3 x^{2}) + 6 x^{2} (- 5 x) + 6 x^{2} \cdot - 2 + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.2

Simplify.

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Step 8.1.3.2.1

Rewrite using the commutative property of multiplication.

$\frac{6 \cdot 3 x^{2} x^{2} + 6 x^{2} (- 5 x) + 6 x^{2} \cdot - 2 + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.2.2

Rewrite using the commutative property of multiplication.

$\frac{6 \cdot 3 x^{2} x^{2} + 6 \cdot - 5 x^{2} x + 6 x^{2} \cdot - 2 + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.2.3

Multiply $- 2$ by $6$ .

$\frac{6 \cdot 3 x^{2} x^{2} + 6 \cdot - 5 x^{2} x - 12 x^{2} + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.3

Simplify each term.

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Step 8.1.3.3.1

Multiply $x^{2}$ by $x^{2}$ by adding the exponents.

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Step 8.1.3.3.1.1

Move $x^{2}$ .

$\frac{6 \cdot 3 (x^{2} x^{2}) + 6 \cdot - 5 x^{2} x - 12 x^{2} + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.3.1.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{6 \cdot 3 x^{2 + 2} + 6 \cdot - 5 x^{2} x - 12 x^{2} + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.3.1.3

Add $2$ and $2$ .

$\frac{6 \cdot 3 x^{4} + 6 \cdot - 5 x^{2} x - 12 x^{2} + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.3.2

Multiply $6$ by $3$ .

$\frac{18 x^{4} + 6 \cdot - 5 x^{2} x - 12 x^{2} + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.3.3

Multiply $x^{2}$ by $x$ by adding the exponents.

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Step 8.1.3.3.3.1

Move $x$ .

$\frac{18 x^{4} + 6 \cdot - 5 (x \cdot x^{2}) - 12 x^{2} + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.3.3.2

Multiply $x$ by $x^{2}$ .

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Step 8.1.3.3.3.2.1

Raise $x$ to the power of $1$ .

$\frac{18 x^{4} + 6 \cdot - 5 (x^{1} x^{2}) - 12 x^{2} + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.3.3.2.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{18 x^{4} + 6 \cdot - 5 x^{1 + 2} - 12 x^{2} + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.3.3.3

Add $1$ and $2$ .

$\frac{18 x^{4} + 6 \cdot - 5 x^{3} - 12 x^{2} + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.3.4

Multiply $6$ by $- 5$ .

$\frac{18 x^{4} - 30 x^{3} - 12 x^{2} + x (3 x^{2} - 5 x - 2) + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.4

Apply the distributive property.

$\frac{18 x^{4} - 30 x^{3} - 12 x^{2} + x (3 x^{2}) + x (- 5 x) + x \cdot - 2 + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.5

Simplify.

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Step 8.1.3.5.1

Rewrite using the commutative property of multiplication.

$\frac{18 x^{4} - 30 x^{3} - 12 x^{2} + 3 x \cdot x^{2} + x (- 5 x) + x \cdot - 2 + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.5.2

Rewrite using the commutative property of multiplication.

$\frac{18 x^{4} - 30 x^{3} - 12 x^{2} + 3 x \cdot x^{2} - 5 x \cdot x + x \cdot - 2 + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.5.3

Move $- 2$ to the left of $x$ .

$\frac{18 x^{4} - 30 x^{3} - 12 x^{2} + 3 x \cdot x^{2} - 5 x \cdot x - 2 \cdot x + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.6

Simplify each term.

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Step 8.1.3.6.1

Multiply $x$ by $x^{2}$ by adding the exponents.

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Step 8.1.3.6.1.1

Move $x^{2}$ .

$\frac{18 x^{4} - 30 x^{3} - 12 x^{2} + 3 (x^{2} x) - 5 x \cdot x - 2 \cdot x + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.6.1.2

Multiply $x^{2}$ by $x$ .

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Step 8.1.3.6.1.2.1

Raise $x$ to the power of $1$ .

$\frac{18 x^{4} - 30 x^{3} - 12 x^{2} + 3 (x^{2} x^{1}) - 5 x \cdot x - 2 \cdot x + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.6.1.2.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{18 x^{4} - 30 x^{3} - 12 x^{2} + 3 x^{2 + 1} - 5 x \cdot x - 2 \cdot x + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.6.1.3

Add $2$ and $1$ .

$\frac{18 x^{4} - 30 x^{3} - 12 x^{2} + 3 x^{3} - 5 x \cdot x - 2 \cdot x + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.6.2

Multiply $x$ by $x$ by adding the exponents.

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Step 8.1.3.6.2.1

Move $x$ .

$\frac{18 x^{4} - 30 x^{3} - 12 x^{2} + 3 x^{3} - 5 (x \cdot x) - 2 \cdot x + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.3.6.2.2

Multiply $x$ by $x$ .

$\frac{18 x^{4} - 30 x^{3} - 12 x^{2} + 3 x^{3} - 5 x^{2} - 2 \cdot x + 12}{3 x^{2} - 5 x - 2}$

$\frac{18 x^{4} - 30 x^{3} - 12 x^{2} + 3 x^{3} - 5 x^{2} - 2 x + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.4

Simplify by adding terms.

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Step 8.1.4.1

Add $- 30 x^{3}$ and $3 x^{3}$ .

$\frac{18 x^{4} - 27 x^{3} - 12 x^{2} - 5 x^{2} - 2 x + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.4.2

Subtract $5 x^{2}$ from $- 12 x^{2}$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} - 5 x - 2}$

Step 8.1.5

Factor by grouping.

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Step 8.1.5.1

For a polynomial of the form $a x^{2} + b x + c$ , rewrite the middle term as a sum of two terms whose product is $a \cdot c = 3 \cdot - 2 = - 6$ and whose sum is $b = - 5$ .

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Step 8.1.5.1.1

Factor $- 5$ out of $- 5 x$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} - 5 (x) - 2}$

Step 8.1.5.1.2

Rewrite $- 5$ as $1$ plus $- 6$

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} + (1 - 6) x - 2}$

Step 8.1.5.1.3

Apply the distributive property.

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} + 1 x - 6 x - 2}$

Step 8.1.5.1.4

Multiply $x$ by $1$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} + x - 6 x - 2}$

Step 8.1.5.2

Factor out the greatest common factor from each group.

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Step 8.1.5.2.1

Group the first two terms and the last two terms.

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{(3 x^{2} + x) - 6 x - 2}$

Step 8.1.5.2.2

Factor out the greatest common factor (GCF) from each group.

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{x (3 x + 1) - 2 (3 x + 1)}$

Step 8.1.5.3

Factor the polynomial by factoring out the greatest common factor, $3 x + 1$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{(3 x + 1) (x - 2)}$

Step 8.1.6

Simplify.

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} - 5 x - 2}$

Step 8.2

Factor by grouping.

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Step 8.2.1

For a polynomial of the form $a x^{2} + b x + c$ , rewrite the middle term as a sum of two terms whose product is $a \cdot c = 3 \cdot - 2 = - 6$ and whose sum is $b = - 5$ .

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Step 8.2.1.1

Factor $- 5$ out of $- 5 x$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} - 5 (x) - 2}$

Step 8.2.1.2

Rewrite $- 5$ as $1$ plus $- 6$

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} + (1 - 6) x - 2}$

Step 8.2.1.3

Apply the distributive property.

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} + 1 x - 6 x - 2}$

Step 8.2.1.4

Multiply $x$ by $1$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} + x - 6 x - 2}$

Step 8.2.2

Factor out the greatest common factor from each group.

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Step 8.2.2.1

Group the first two terms and the last two terms.

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{(3 x^{2} + x) - 6 x - 2}$

Step 8.2.2.2

Factor out the greatest common factor (GCF) from each group.

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{x (3 x + 1) - 2 (3 x + 1)}$

Step 8.2.3

Factor the polynomial by factoring out the greatest common factor, $3 x + 1$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{(3 x + 1) (x - 2)}$

Step 8.3

Expand $(3 x + 1) (x - 2)$ .

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Step 8.3.1

Apply the distributive property.

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x (x - 2) + 1 (x - 2)}$

Step 8.3.2

Apply the distributive property.

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x \cdot x + 3 x \cdot - 2 + 1 (x - 2)}$

Step 8.3.3

Apply the distributive property.

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x \cdot x + 3 x \cdot - 2 + 1 x + 1 \cdot - 2}$

Step 8.3.4

Move $x$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x \cdot x + 3 \cdot (- 2 x) + 1 x + 1 \cdot - 2}$

Step 8.3.5

Raise $x$ to the power of $1$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 (x \cdot x) + 3 \cdot (- 2 x) + 1 x + 1 \cdot - 2}$

Step 8.3.6

Raise $x$ to the power of $1$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 (x \cdot x) + 3 \cdot (- 2 x) + 1 x + 1 \cdot - 2}$

Step 8.3.7

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{1 + 1} + 3 \cdot (- 2 x) + 1 x + 1 \cdot - 2}$

Step 8.3.8

Add $1$ and $1$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} + 3 \cdot (- 2 x) + 1 x + 1 \cdot - 2}$

Step 8.3.9

Multiply $3$ by $- 2$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} - 6 x + 1 x + 1 \cdot - 2}$

Step 8.3.10

Multiply $x$ by $1$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} - 6 x + x + 1 \cdot - 2}$

Step 8.3.11

Multiply $- 2$ by $1$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} - 6 x + x - 2}$

Step 8.3.12

Add $- 6 x$ and $x$ .

$\frac{18 x^{4} - 27 x^{3} - 17 x^{2} - 2 x + 12}{3 x^{2} - 5 x - 2}$

Step 8.4

Set up the polynomials to be divided. If there is not a term for every exponent, insert one with a value of $0$ .

$3 x^{2}$

$5 x$

$2$

$18 x^{4}$

$27 x^{3}$

$17 x^{2}$

$2 x$

$12$

Step 8.5

Divide the highest order term in the dividend $18 x^{4}$ by the highest order term in divisor $3 x^{2}$ .

							$6 x^{2}$
	$3 x^{2}$	-	$5 x$	-	$2$		$18 x^{4}$	-	$27 x^{3}$	-	$17 x^{2}$	-	$2 x$	+	$12$

Step 8.6

Multiply the new quotient term by the divisor.

						$6 x^{2}$
$3 x^{2}$	-	$5 x$	-	$2$		$18 x^{4}$	-	$27 x^{3}$	-	$17 x^{2}$	-	$2 x$	+	$12$
					+	$18 x^{4}$	-	$30 x^{3}$	-	$12 x^{2}$

Step 8.7

The expression needs to be subtracted from the dividend, so change all the signs in $18 x^{4} - 30 x^{3} - 12 x^{2}$

$6 x^{2}$

$3 x^{2}$

$5 x$

$2$

$18 x^{4}$

$27 x^{3}$

$17 x^{2}$

$2 x$

$12$

$18 x^{4}$

$30 x^{3}$

$12 x^{2}$

Step 8.8

After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.

$6 x^{2}$

$3 x^{2}$

$5 x$

$2$

$18 x^{4}$

$27 x^{3}$

$17 x^{2}$

$2 x$

$12$

$18 x^{4}$

$30 x^{3}$

$12 x^{2}$

$3 x^{3}$

$5 x^{2}$

Step 8.9

Pull the next terms from the original dividend down into the current dividend.

$6 x^{2}$

$3 x^{2}$

$5 x$

$2$

$18 x^{4}$

$27 x^{3}$

$17 x^{2}$

$2 x$

$12$

$18 x^{4}$

$30 x^{3}$

$12 x^{2}$

$3 x^{3}$

$5 x^{2}$

$2 x$

Step 8.10

Divide the highest order term in the dividend $3 x^{3}$ by the highest order term in divisor $3 x^{2}$ .

$6 x^{2}$

$x$

$3 x^{2}$

$5 x$

$2$

$18 x^{4}$

$27 x^{3}$

$17 x^{2}$

$2 x$

$12$

$18 x^{4}$

$30 x^{3}$

$12 x^{2}$

$3 x^{3}$

$5 x^{2}$

$2 x$

Step 8.11

Multiply the new quotient term by the divisor.

$6 x^{2}$

$x$

$3 x^{2}$

$5 x$

$2$

$18 x^{4}$

$27 x^{3}$

$17 x^{2}$

$2 x$

$12$

$18 x^{4}$

$30 x^{3}$

$12 x^{2}$

$3 x^{3}$

$5 x^{2}$

$2 x$

$3 x^{3}$

$5 x^{2}$

$2 x$

Step 8.12

The expression needs to be subtracted from the dividend, so change all the signs in $3 x^{3} - 5 x^{2} - 2 x$

$6 x^{2}$

$x$

$3 x^{2}$

$5 x$

$2$

$18 x^{4}$

$27 x^{3}$

$17 x^{2}$

$2 x$

$12$

$18 x^{4}$

$30 x^{3}$

$12 x^{2}$

$3 x^{3}$

$5 x^{2}$

$2 x$

$3 x^{3}$

$5 x^{2}$

$2 x$

Step 8.13

After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.

$6 x^{2}$

$x$

$3 x^{2}$

$5 x$

$2$

$18 x^{4}$

$27 x^{3}$

$17 x^{2}$

$2 x$

$12$

$18 x^{4}$

$30 x^{3}$

$12 x^{2}$

$3 x^{3}$

$5 x^{2}$

$2 x$

$3 x^{3}$

$5 x^{2}$

$2 x$

$0$

Step 8.14

Pull the next terms from the original dividend down into the current dividend.

$6 x^{2}$

$x$

$3 x^{2}$

$5 x$

$2$

$18 x^{4}$

$27 x^{3}$

$17 x^{2}$

$2 x$

$12$

$18 x^{4}$

$30 x^{3}$

$12 x^{2}$

$3 x^{3}$

$5 x^{2}$

$2 x$

$3 x^{3}$

$5 x^{2}$

$2 x$

$0$

$12$

Step 8.15

The final answer is the quotient plus the remainder over the divisor.

$6 x^{2} + x + \frac{12}{3 x^{2} - 5 x - 2}$

Step 8.16

The oblique asymptote is the polynomial portion of the long division result.

$y = 6 x^{2} + x$

Step 9

This is the set of all asymptotes.

Vertical Asymptotes: $x = - \frac{1}{3}, 2$

No Horizontal Asymptotes

Oblique Asymptotes: $y = 6 x^{2} + x$

Step 10