Finite Math Examples

$\frac{3 x^{3} - 81}{4 x^{2} + 8 x - 60} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 1

Simplify the numerator.

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Step 1.1

Factor $3$ out of $3 x^{3} - 81$ .

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Step 1.1.1

Factor $3$ out of $3 x^{3}$ .

$\frac{3 (x^{3}) - 81}{4 x^{2} + 8 x - 60} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 1.1.2

Factor $3$ out of $- 81$ .

$\frac{3 x^{3} + 3 \cdot - 27}{4 x^{2} + 8 x - 60} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 1.1.3

Factor $3$ out of $3 x^{3} + 3 \cdot - 27$ .

$\frac{3 (x^{3} - 27)}{4 x^{2} + 8 x - 60} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 1.2

Rewrite $27$ as $3^{3}$ .

$\frac{3 (x^{3} - 3^{3})}{4 x^{2} + 8 x - 60} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 1.3

Since both terms are perfect cubes, factor using the difference of cubes formula, $a^{3} - b^{3} = (a - b) (a^{2} + a b + b^{2})$ where $a = x$ and $b = 3$ .

$\frac{3 ((x - 3) (x^{2} + x \cdot 3 + 3^{2}))}{4 x^{2} + 8 x - 60} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 1.4

Simplify.

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Step 1.4.1

Move $3$ to the left of $x$ .

$\frac{3 ((x - 3) (x^{2} + 3 \cdot x + 3^{2}))}{4 x^{2} + 8 x - 60} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 1.4.2

Raise $3$ to the power of $2$ .

$\frac{3 ((x - 3) (x^{2} + 3 x + 9))}{4 x^{2} + 8 x - 60} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 x^{2} + 8 x - 60} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 2

Simplify the denominator.

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Step 2.1

Factor $4$ out of $4 x^{2} + 8 x - 60$ .

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Step 2.1.1

Factor $4$ out of $4 x^{2}$ .

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 (x^{2}) + 8 x - 60} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 2.1.2

Factor $4$ out of $8 x$ .

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 (x^{2}) + 4 (2 x) - 60} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 2.1.3

Factor $4$ out of $- 60$ .

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 x^{2} + 4 (2 x) + 4 \cdot - 15} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 2.1.4

Factor $4$ out of $4 x^{2} + 4 (2 x)$ .

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 (x^{2} + 2 x) + 4 \cdot - 15} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 2.1.5

Factor $4$ out of $4 (x^{2} + 2 x) + 4 \cdot - 15$ .

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 (x^{2} + 2 x - 15)} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 2.2

Factor $x^{2} + 2 x - 15$ using the AC method.

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Step 2.2.1

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 $- 15$ and whose sum is $2$ .

$- 3, 5$

Step 2.2.2

Write the factored form using these integers.

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 ((x - 3) (x + 5))} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 (x - 3) (x + 5)} \cdot \frac{8 x + 16}{6 x^{2} + 18 x + 54}$

Step 3

Simplify terms.

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Step 3.1

Factor $8$ out of $8 x + 16$ .

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Step 3.1.1

Factor $8$ out of $8 x$ .

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 (x - 3) (x + 5)} \cdot \frac{8 (x) + 16}{6 x^{2} + 18 x + 54}$

Step 3.1.2

Factor $8$ out of $16$ .

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 (x - 3) (x + 5)} \cdot \frac{8 x + 8 \cdot 2}{6 x^{2} + 18 x + 54}$

Step 3.1.3

Factor $8$ out of $8 x + 8 \cdot 2$ .

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 (x - 3) (x + 5)} \cdot \frac{8 (x + 2)}{6 x^{2} + 18 x + 54}$

Step 3.2

Factor $6$ out of $6 x^{2} + 18 x + 54$ .

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Step 3.2.1

Factor $6$ out of $6 x^{2}$ .

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 (x - 3) (x + 5)} \cdot \frac{8 (x + 2)}{6 (x^{2}) + 18 x + 54}$

Step 3.2.2

Factor $6$ out of $18 x$ .

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 (x - 3) (x + 5)} \cdot \frac{8 (x + 2)}{6 (x^{2}) + 6 (3 x) + 54}$

Step 3.2.3

Factor $6$ out of $54$ .

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 (x - 3) (x + 5)} \cdot \frac{8 (x + 2)}{6 x^{2} + 6 (3 x) + 6 \cdot 9}$

Step 3.2.4

Factor $6$ out of $6 x^{2} + 6 (3 x)$ .

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 (x - 3) (x + 5)} \cdot \frac{8 (x + 2)}{6 (x^{2} + 3 x) + 6 \cdot 9}$

Step 3.2.5

Factor $6$ out of $6 (x^{2} + 3 x) + 6 \cdot 9$ .

$\frac{3 (x - 3) (x^{2} + 3 x + 9)}{4 (x - 3) (x + 5)} \cdot \frac{8 (x + 2)}{6 (x^{2} + 3 x + 9)}$

Step 3.3

Combine.

$\frac{3 (x - 3) (x^{2} + 3 x + 9) (8 (x + 2))}{4 (x - 3) (x + 5) (6 (x^{2} + 3 x + 9))}$

Step 3.4

Cancel the common factor of $3$ and $6$ .

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Step 3.4.1

Factor $3$ out of $3 (x - 3) (x^{2} + 3 x + 9) (8 (x + 2))$ .

$\frac{3 (((x - 3) (x^{2} + 3 x + 9)) (8 (x + 2)))}{4 (x - 3) (x + 5) (6 (x^{2} + 3 x + 9))}$

Step 3.4.2

Cancel the common factors.

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Step 3.4.2.1

Factor $3$ out of $4 (x - 3) (x + 5) (6 (x^{2} + 3 x + 9))$ .

$\frac{3 (((x - 3) (x^{2} + 3 x + 9)) (8 (x + 2)))}{3 (4 (x - 3) (x + 5) (2 (x^{2} + 3 x + 9)))}$

Step 3.4.2.2

Cancel the common factor.

$\frac{3 (((x - 3) (x^{2} + 3 x + 9)) (8 (x + 2)))}{3 (4 (x - 3) (x + 5) (2 (x^{2} + 3 x + 9)))}$

Step 3.4.2.3

Rewrite the expression.

$\frac{((x - 3) (x^{2} + 3 x + 9)) (8 (x + 2))}{4 (x - 3) (x + 5) (2 (x^{2} + 3 x + 9))}$

Step 3.5

Cancel the common factor of $x - 3$ .

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Step 3.5.1

Cancel the common factor.

$\frac{(x - 3) (x^{2} + 3 x + 9) (8 (x + 2))}{4 (x - 3) (x + 5) (2 (x^{2} + 3 x + 9))}$

Step 3.5.2

Rewrite the expression.

$\frac{(x^{2} + 3 x + 9) (8 (x + 2))}{(4 (x + 5)) (2 (x^{2} + 3 x + 9))}$

Step 3.6

Cancel the common factor of $x^{2} + 3 x + 9$ .

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Step 3.6.1

Cancel the common factor.

$\frac{(x^{2} + 3 x + 9) (8 (x + 2))}{4 (x + 5) (2 (x^{2} + 3 x + 9))}$

Step 3.6.2

Rewrite the expression.

$\frac{8 (x + 2)}{(4 (x + 5)) \cdot (2)}$

Step 3.7

Cancel the common factor of $8$ and $4$ .

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Step 3.7.1

Factor $4$ out of $8 (x + 2)$ .

$\frac{4 (2 (x + 2))}{(4 (x + 5)) \cdot (2)}$

Step 3.7.2

Cancel the common factors.

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Step 3.7.2.1

Factor $4$ out of $(4 (x + 5)) \cdot (2)$ .

$\frac{4 (2 (x + 2))}{4 ((x + 5) \cdot (2))}$

Step 3.7.2.2

Cancel the common factor.

$\frac{4 (2 (x + 2))}{4 ((x + 5) \cdot (2))}$

Step 3.7.2.3

Rewrite the expression.

$\frac{2 (x + 2)}{(x + 5) \cdot (2)}$

Step 3.8

Cancel the common factor of $2$ .

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Step 3.8.1

Cancel the common factor.

$\frac{2 (x + 2)}{(x + 5) \cdot 2}$

Step 3.8.2

Rewrite the expression.

$\frac{x + 2}{x + 5}$