Algebra Examples

$\frac{- 4}{9 - x^{2}} \cdot \frac{x^{2} - 9}{24 x - 4 x^{2}} \cdot \frac{x^{2} - 36}{x^{2} + 9 x + 18}$

Step 1

Simplify the numerator.

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Step 1.1

Rewrite $36$ as $6^{2}$ .

$\frac{- 4}{9 - x^{2}} \cdot \frac{x^{2} - 9}{24 x - 4 x^{2}} \cdot \frac{x^{2} - 6^{2}}{x^{2} + 9 x + 18}$

Step 1.2

Since both terms are perfect squares, factor using the difference of squares formula, $a^{2} - b^{2} = (a + b) (a - b)$ where $a = x$ and $b = 6$ .

$\frac{- 4}{9 - x^{2}} \cdot \frac{x^{2} - 9}{24 x - 4 x^{2}} \cdot \frac{(x + 6) (x - 6)}{x^{2} + 9 x + 18}$

Step 2

Factor $x^{2} + 9 x + 18$ using the AC method.

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Step 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 $18$ and whose sum is $9$ .

$3, 6$

Step 2.2

Write the factored form using these integers.

$\frac{- 4}{9 - x^{2}} \cdot \frac{x^{2} - 9}{24 x - 4 x^{2}} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 3

Simplify the denominator.

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Step 3.1

Rewrite $9$ as $3^{2}$ .

$\frac{- 4}{3^{2} - x^{2}} \cdot \frac{x^{2} - 9}{24 x - 4 x^{2}} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 3.2

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

$\frac{- 4}{(3 + x) (3 - x)} \cdot \frac{x^{2} - 9}{24 x - 4 x^{2}} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 4

Simplify the numerator.

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Step 4.1

Rewrite $9$ as $3^{2}$ .

$\frac{- 4}{(3 + x) (3 - x)} \cdot \frac{x^{2} - 3^{2}}{24 x - 4 x^{2}} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 4.2

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

$\frac{- 4}{(3 + x) (3 - x)} \cdot \frac{(x + 3) (x - 3)}{24 x - 4 x^{2}} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 5

Simplify terms.

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Step 5.1

Factor $4 x$ out of $24 x - 4 x^{2}$ .

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Step 5.1.1

Factor $4 x$ out of $24 x$ .

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

Step 5.1.2

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

$\frac{- 4}{(3 + x) (3 - x)} \cdot \frac{(x + 3) (x - 3)}{4 x (6) + 4 x (- x)} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 5.1.3

Factor $4 x$ out of $4 x (6) + 4 x (- x)$ .

$\frac{- 4}{(3 + x) (3 - x)} \cdot \frac{(x + 3) (x - 3)}{4 x (6 - x)} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 5.2

Cancel the common factor of $4$ .

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Step 5.2.1

Factor $4$ out of $- 4$ .

$\frac{4 (- 1)}{(3 + x) (3 - x)} \cdot \frac{(x + 3) (x - 3)}{4 x (6 - x)} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 5.2.2

Factor $4$ out of $4 x (6 - x)$ .

$\frac{4 (- 1)}{(3 + x) (3 - x)} \cdot \frac{(x + 3) (x - 3)}{4 (x (6 - x))} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 5.2.3

Cancel the common factor.

$\frac{4 \cdot - 1}{(3 + x) (3 - x)} \cdot \frac{(x + 3) (x - 3)}{4 (x (6 - x))} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 5.2.4

Rewrite the expression.

$\frac{- 1}{(3 + x) (3 - x)} \cdot \frac{(x + 3) (x - 3)}{x (6 - x)} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 5.3

Multiply $\frac{- 1}{(3 + x) (3 - x)}$ by $\frac{(x + 3) (x - 3)}{x (6 - x)}$ .

$\frac{- ((x + 3) (x - 3))}{(3 + x) (3 - x) (x (6 - x))} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 5.4

Cancel the common factor of $x + 3$ .

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Step 5.4.1

Factor $x + 3$ out of $- (x + 3) (x - 3)$ .

$\frac{(x + 3) (- 1 (x - 3))}{(3 + x) (3 - x) x (6 - x)} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 5.4.2

Cancel the common factor.

$\frac{(x + 3) (- 1 (x - 3))}{(3 + x) (3 - x) x (6 - x)} \cdot \frac{(x + 6) (x - 6)}{(x + 3) (x + 6)}$

Step 5.4.3

Rewrite the expression.

$\frac{- 1 (x - 3)}{(3 + x) (3 - x) x (6 - x)} \cdot \frac{(x + 6) (x - 6)}{x + 6}$

Step 5.5

Multiply $\frac{- 1 (x - 3)}{(3 + x) (3 - x) x (6 - x)}$ by $\frac{(x + 6) (x - 6)}{x + 6}$ .

$\frac{- 1 (x - 3) ((x + 6) (x - 6))}{(3 + x) (3 - x) x (6 - x) (x + 6)}$

Step 5.6

Cancel the common factor of $x + 6$ .

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Step 5.6.1

Cancel the common factor.

$\frac{- 1 (x - 3) ((x + 6) (x - 6))}{(3 + x) (3 - x) x (6 - x) (x + 6)}$

Step 5.6.2

Rewrite the expression.

$\frac{- 1 (x - 3) (x - 6)}{(3 + x) (3 - x) x (6 - x)}$

Step 5.7

Cancel the common factor of $x - 3$ and $3 - x$ .

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Step 5.7.1

Factor $- 1$ out of $x$ .

$\frac{- 1 (- 1 (- x) - 3) (x - 6)}{(3 + x) (3 - x) x (6 - x)}$

Step 5.7.2

Rewrite $- 3$ as $- 1 (3)$ .

$\frac{- 1 (- 1 (- x) - 1 (3)) (x - 6)}{(3 + x) (3 - x) x (6 - x)}$

Step 5.7.3

Factor $- 1$ out of $- 1 (- x) - 1 (3)$ .

$\frac{- 1 (- 1 (- x + 3)) (x - 6)}{(3 + x) (3 - x) x (6 - x)}$

Step 5.7.4

Reorder terms.

$\frac{- 1 (- 1 (- x + 3)) (x - 6)}{(3 + x) (- x + 3) x (6 - x)}$

Step 5.7.5

Cancel the common factor.

$\frac{- 1 (- 1 (- x + 3)) (x - 6)}{(3 + x) (- x + 3) x (6 - x)}$

Step 5.7.6

Rewrite the expression.

$\frac{- 1 \cdot (- 1) (x - 6)}{(3 + x) x (6 - x)}$

Step 5.8

Cancel the common factor of $x - 6$ and $6 - x$ .

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Step 5.8.1

Factor $- 1$ out of $x$ .

$\frac{- 1 \cdot (- 1) (- 1 (- x) - 6)}{(3 + x) x (6 - x)}$

Step 5.8.2

Rewrite $- 6$ as $- 1 (6)$ .

$\frac{- 1 \cdot (- 1) (- 1 (- x) - 1 (6))}{(3 + x) x (6 - x)}$

Step 5.8.3

Factor $- 1$ out of $- 1 (- x) - 1 (6)$ .

$\frac{- 1 \cdot (- 1) (- 1 (- x + 6))}{(3 + x) x (6 - x)}$

Step 5.8.4

Reorder terms.

$\frac{- 1 \cdot (- 1) (- 1 (- x + 6))}{(3 + x) x (- x + 6)}$

Step 5.8.5

Cancel the common factor.

$\frac{- 1 \cdot (- 1) (- 1 (- x + 6))}{(3 + x) x (- x + 6)}$

Step 5.8.6

Rewrite the expression.

$\frac{- 1 \cdot (- 1) \cdot (- 1)}{(3 + x) x}$

Step 6

Simplify the numerator.

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Step 6.1

Multiply $- 1$ by $- 1$ .

$\frac{1 \cdot - 1}{(3 + x) x}$

Step 6.2

Multiply $- 1$ by $1$ .

$\frac{- 1}{(3 + x) x}$

Step 7

Simplify the expression.

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Step 7.1

Move the negative in front of the fraction.

$- \frac{1}{(3 + x) x}$

Step 7.2

Reorder factors in $- \frac{1}{(3 + x) x}$ .

$- \frac{1}{x (3 + x)}$