Pre-Algebra Examples

$\frac{8}{x^{2} - 36} - \frac{2}{x^{2} + 12 x + 36}$

Step 1

Simplify each term.

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Step 1.1

Simplify the denominator.

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Step 1.1.1

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

$\frac{8}{x^{2} - 6^{2}} - \frac{2}{x^{2} + 12 x + 36}$

Step 1.1.2

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 $b = 6$ .

$\frac{8}{(x + 6) (x - 6)} - \frac{2}{x^{2} + 12 x + 36}$

Step 1.2

Factor using the perfect square rule.

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Step 1.2.1

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

$\frac{8}{(x + 6) (x - 6)} - \frac{2}{x^{2} + 12 x + 6^{2}}$

Step 1.2.2

Check that the middle term is two times the product of the numbers being squared in the first term and third term.

$12 x = 2 \cdot x \cdot 6$

Step 1.2.3

Rewrite the polynomial.

$\frac{8}{(x + 6) (x - 6)} - \frac{2}{x^{2} + 2 \cdot x \cdot 6 + 6^{2}}$

Step 1.2.4

Factor using the perfect square trinomial rule $a^{2} + 2 a b + b^{2} = {(a + b)}^{2}$ , where $a = x$ and $b = 6$ .

$\frac{8}{(x + 6) (x - 6)} - \frac{2}{{(x + 6)}^{2}}$

Step 2

To write $\frac{8}{(x + 6) (x - 6)}$ as a fraction with a common denominator, multiply by $\frac{x + 6}{x + 6}$ .

$\frac{8}{(x + 6) (x - 6)} \cdot \frac{x + 6}{x + 6} - \frac{2}{{(x + 6)}^{2}}$

Step 3

To write $- \frac{2}{{(x + 6)}^{2}}$ as a fraction with a common denominator, multiply by $\frac{x - 6}{x - 6}$ .

$\frac{8}{(x + 6) (x - 6)} \cdot \frac{x + 6}{x + 6} - \frac{2}{{(x + 6)}^{2}} \cdot \frac{x - 6}{x - 6}$

Step 4

Write each expression with a common denominator of $(x - 6) {(x + 6)}^{2}$ , by multiplying each by an appropriate factor of $1$ .

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Step 4.1

Multiply $\frac{8}{(x + 6) (x - 6)}$ by $\frac{x + 6}{x + 6}$ .

$\frac{8 (x + 6)}{(x + 6) (x - 6) (x + 6)} - \frac{2}{{(x + 6)}^{2}} \cdot \frac{x - 6}{x - 6}$

Step 4.2

Raise $x + 6$ to the power of $1$ .

$\frac{8 (x + 6)}{{(x + 6)}^{1} (x + 6) (x - 6)} - \frac{2}{{(x + 6)}^{2}} \cdot \frac{x - 6}{x - 6}$

Step 4.3

Raise $x + 6$ to the power of $1$ .

$\frac{8 (x + 6)}{{(x + 6)}^{1} {(x + 6)}^{1} (x - 6)} - \frac{2}{{(x + 6)}^{2}} \cdot \frac{x - 6}{x - 6}$

Step 4.4

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

$\frac{8 (x + 6)}{{(x + 6)}^{1 + 1} (x - 6)} - \frac{2}{{(x + 6)}^{2}} \cdot \frac{x - 6}{x - 6}$

Step 4.5

Add $1$ and $1$ .

$\frac{8 (x + 6)}{{(x + 6)}^{2} (x - 6)} - \frac{2}{{(x + 6)}^{2}} \cdot \frac{x - 6}{x - 6}$

Step 4.6

Multiply $\frac{2}{{(x + 6)}^{2}}$ by $\frac{x - 6}{x - 6}$ .

$\frac{8 (x + 6)}{{(x + 6)}^{2} (x - 6)} - \frac{2 (x - 6)}{{(x + 6)}^{2} (x - 6)}$

Step 5

Combine the numerators over the common denominator.

$\frac{8 (x + 6) - 2 (x - 6)}{{(x + 6)}^{2} (x - 6)}$

Step 6

Simplify the numerator.

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Step 6.1

Factor $2$ out of $8 (x + 6) - 2 (x - 6)$ .

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Step 6.1.1

Factor $2$ out of $8 (x + 6)$ .

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

Step 6.1.2

Factor $2$ out of $- 2 (x - 6)$ .

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

Step 6.1.3

Factor $2$ out of $2 (4 (x + 6)) + 2 (- (x - 6))$ .

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

Step 6.2

Apply the distributive property.

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

Step 6.3

Multiply $4$ by $6$ .

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

Step 6.4

Apply the distributive property.

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

Step 6.5

Multiply $- 1$ by $- 6$ .

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

Step 6.6

Subtract $x$ from $4 x$ .

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

Step 6.7

Add $24$ and $6$ .

$\frac{2 (3 x + 30)}{{(x + 6)}^{2} (x - 6)}$

Step 6.8

Factor $3$ out of $3 x + 30$ .

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Step 6.8.1

Factor $3$ out of $3 x$ .

$\frac{2 (3 (x) + 30)}{{(x + 6)}^{2} (x - 6)}$

Step 6.8.2

Factor $3$ out of $30$ .

$\frac{2 (3 x + 3 \cdot 10)}{{(x + 6)}^{2} (x - 6)}$

Step 6.8.3

Factor $3$ out of $3 x + 3 \cdot 10$ .

$\frac{2 (3 (x + 10))}{{(x + 6)}^{2} (x - 6)}$

$\frac{2 \cdot 3 (x + 10)}{{(x + 6)}^{2} (x - 6)}$

Step 6.9

Multiply $2$ by $3$ .

$\frac{6 (x + 10)}{{(x + 6)}^{2} (x - 6)}$