Finite Math Examples

$f (x) = \frac{x^{4} + 1}{x^{2} + 5 x - 14}$

Step 1

Find where the expression $\frac{x^{4} + 1}{x^{2} + 5 x - 14}$ is undefined.

$x = - 7, x = 2$

Step 2

Since $\frac{x^{4} + 1}{x^{2} + 5 x - 14}$ $\to$ $\infty$ as $x$ $\to$ $- 7$ from the left and $\frac{x^{4} + 1}{x^{2} + 5 x - 14}$ $\to$ $- \infty$ as $x$ $\to$ $- 7$ from the right, then $x = - 7$ is a vertical asymptote.

$x = - 7$

Step 3

Since $\frac{x^{4} + 1}{x^{2} + 5 x - 14}$ $\to$ $- \infty$ as $x$ $\to$ $2$ from the left and $\frac{x^{4} + 1}{x^{2} + 5 x - 14}$ $\to$ $\infty$ as $x$ $\to$ $2$ from the right, then $x = 2$ is a vertical asymptote.

$x = 2$

Step 4

List all of the vertical asymptotes:

$x = - 7, 2$

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

Factor $x^{2} + 5 x - 14$ using the AC method.

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Step 8.1.1

Consider the form $x^{2} + b x + c$ . Find a pair of integers whose product is $c$ and whose sum is $b$ . In this case, whose product is $- 14$ and whose sum is $5$ .

$- 2, 7$

Step 8.1.2

Write the factored form using these integers.

$\frac{x^{4} + 1}{(x - 2) (x + 7)}$

Step 8.2

Expand $(x - 2) (x + 7)$ .

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Step 8.2.1

Apply the distributive property.

$\frac{x^{4} + 1}{x (x + 7) - 2 (x + 7)}$

Step 8.2.2

Apply the distributive property.

$\frac{x^{4} + 1}{x \cdot x + x \cdot 7 - 2 (x + 7)}$

Step 8.2.3

Apply the distributive property.

$\frac{x^{4} + 1}{x \cdot x + x \cdot 7 - 2 x - 2 \cdot 7}$

Step 8.2.4

Reorder $x$ and $7$ .

$\frac{x^{4} + 1}{x \cdot x + 7 x - 2 x - 2 \cdot 7}$

Step 8.2.5

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

$\frac{x^{4} + 1}{x \cdot x + 7 x - 2 x - 2 \cdot 7}$

Step 8.2.6

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

$\frac{x^{4} + 1}{x \cdot x + 7 x - 2 x - 2 \cdot 7}$

Step 8.2.7

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

$\frac{x^{4} + 1}{x^{1 + 1} + 7 x - 2 x - 2 \cdot 7}$

Step 8.2.8

Add $1$ and $1$ .

$\frac{x^{4} + 1}{x^{2} + 7 x - 2 x - 2 \cdot 7}$

Step 8.2.9

Multiply $- 2$ by $7$ .

$\frac{x^{4} + 1}{x^{2} + 7 x - 2 x - 14}$

Step 8.2.10

Subtract $2 x$ from $7 x$ .

$\frac{x^{4} + 1}{x^{2} + 5 x - 14}$

Step 8.3

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

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

Step 8.4

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

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

Step 8.5

Multiply the new quotient term by the divisor.

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

$x^{4}$

$5 x^{3}$

$14 x^{2}$

Step 8.6

The expression needs to be subtracted from the dividend, so change all the signs in $x^{4} + 5 x^{3} - 14 x^{2}$

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

$x^{4}$

$5 x^{3}$

$14 x^{2}$

Step 8.7

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

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

$x^{4}$

$5 x^{3}$

$14 x^{2}$

$5 x^{3}$

$14 x^{2}$

Step 8.8

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

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

$x^{4}$

$5 x^{3}$

$14 x^{2}$

$5 x^{3}$

$14 x^{2}$

$0 x$

Step 8.9

Divide the highest order term in the dividend $- 5 x^{3}$ by the highest order term in divisor $x^{2}$ .

$x^{2}$

$5 x$

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

$x^{4}$

$5 x^{3}$

$14 x^{2}$

$5 x^{3}$

$14 x^{2}$

$0 x$

Step 8.10

Multiply the new quotient term by the divisor.

$x^{2}$

$5 x$

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

$x^{4}$

$5 x^{3}$

$14 x^{2}$

$5 x^{3}$

$14 x^{2}$

$0 x$

$5 x^{3}$

$25 x^{2}$

$70 x$

Step 8.11

The expression needs to be subtracted from the dividend, so change all the signs in $- 5 x^{3} - 25 x^{2} + 70 x$

$x^{2}$

$5 x$

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

$x^{4}$

$5 x^{3}$

$14 x^{2}$

$5 x^{3}$

$14 x^{2}$

$0 x$

$5 x^{3}$

$25 x^{2}$

$70 x$

Step 8.12

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

$x^{2}$

$5 x$

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

$x^{4}$

$5 x^{3}$

$14 x^{2}$

$5 x^{3}$

$14 x^{2}$

$0 x$

$5 x^{3}$

$25 x^{2}$

$70 x$

$39 x^{2}$

$70 x$

Step 8.13

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

$x^{2}$

$5 x$

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

$x^{4}$

$5 x^{3}$

$14 x^{2}$

$5 x^{3}$

$14 x^{2}$

$0 x$

$5 x^{3}$

$25 x^{2}$

$70 x$

$39 x^{2}$

$70 x$

$1$

Step 8.14

Divide the highest order term in the dividend $39 x^{2}$ by the highest order term in divisor $x^{2}$ .

$x^{2}$

$5 x$

$39$

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

$x^{4}$

$5 x^{3}$

$14 x^{2}$

$5 x^{3}$

$14 x^{2}$

$0 x$

$5 x^{3}$

$25 x^{2}$

$70 x$

$39 x^{2}$

$70 x$

$1$

Step 8.15

Multiply the new quotient term by the divisor.

$x^{2}$

$5 x$

$39$

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

$x^{4}$

$5 x^{3}$

$14 x^{2}$

$5 x^{3}$

$14 x^{2}$

$0 x$

$5 x^{3}$

$25 x^{2}$

$70 x$

$39 x^{2}$

$70 x$

$1$

$39 x^{2}$

$195 x$

$546$

Step 8.16

The expression needs to be subtracted from the dividend, so change all the signs in $39 x^{2} + 195 x - 546$

$x^{2}$

$5 x$

$39$

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

$x^{4}$

$5 x^{3}$

$14 x^{2}$

$5 x^{3}$

$14 x^{2}$

$0 x$

$5 x^{3}$

$25 x^{2}$

$70 x$

$39 x^{2}$

$70 x$

$1$

$39 x^{2}$

$195 x$

$546$

Step 8.17

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

$x^{2}$

$5 x$

$39$

$x^{2}$

$5 x$

$14$

$x^{4}$

$0 x^{3}$

$0 x^{2}$

$0 x$

$1$

$x^{4}$

$5 x^{3}$

$14 x^{2}$

$5 x^{3}$

$14 x^{2}$

$0 x$

$5 x^{3}$

$25 x^{2}$

$70 x$

$39 x^{2}$

$70 x$

$1$

$39 x^{2}$

$195 x$

$546$

$265 x$

$547$

Step 8.18

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

$x^{2} - 5 x + 39 + \frac{- 265 x + 547}{x^{2} + 5 x - 14}$

Step 8.19

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

$y = x^{2} - 5 x + 39$

Step 9

This is the set of all asymptotes.

Vertical Asymptotes: $x = - 7, 2$

No Horizontal Asymptotes

Oblique Asymptotes: $y = x^{2} - 5 x + 39$

Step 10