Pre-Algebra Examples

$\frac{x^{2} - 6 x + 9}{x^{2} - 4} \div \frac{x^{2} - 9}{x^{2} - 8 x + 12}$

Step 1

To divide by a fraction, multiply by its reciprocal.

$\frac{x^{2} - 6 x + 9}{x^{2} - 4} \cdot \frac{x^{2} - 8 x + 12}{x^{2} - 9}$

Step 2

Factor using the perfect square rule.

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Step 2.1

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

$\frac{x^{2} - 6 x + 3^{2}}{x^{2} - 4} \cdot \frac{x^{2} - 8 x + 12}{x^{2} - 9}$

Step 2.2

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

$6 x = 2 \cdot x \cdot 3$

Step 2.3

Rewrite the polynomial.

$\frac{x^{2} - 2 \cdot x \cdot 3 + 3^{2}}{x^{2} - 4} \cdot \frac{x^{2} - 8 x + 12}{x^{2} - 9}$

Step 2.4

Factor using the perfect square trinomial rule $a^{2} - 2 a b + b^{2} = {(a - b)}^{2}$ , where $a = x$ and $b = 3$ .

$\frac{{(x - 3)}^{2}}{x^{2} - 4} \cdot \frac{x^{2} - 8 x + 12}{x^{2} - 9}$

Step 3

Simplify the denominator.

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Step 3.1

Rewrite $4$ as $2^{2}$ .

$\frac{{(x - 3)}^{2}}{x^{2} - 2^{2}} \cdot \frac{x^{2} - 8 x + 12}{x^{2} - 9}$

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 $a = x$ and $b = 2$ .

$\frac{{(x - 3)}^{2}}{(x + 2) (x - 2)} \cdot \frac{x^{2} - 8 x + 12}{x^{2} - 9}$

Step 4

Factor $x^{2} - 8 x + 12$ using the AC method.

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Step 4.1

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 $12$ and whose sum is $- 8$ .

$- 6, - 2$

Step 4.2

Write the factored form using these integers.

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

Step 5

Simplify the denominator.

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Step 5.1

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

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

Step 5.2

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 $b = 3$ .

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

Step 6

Combine.

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

Step 7

Cancel the common factor of ${(x - 3)}^{2}$ and $x - 3$ .

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Step 7.1

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

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

Step 7.2

Cancel the common factors.

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Step 7.2.1

Factor $x - 3$ out of $(x + 2) (x - 2) ((x + 3) (x - 3))$ .

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

Step 7.2.2

Cancel the common factor.

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

Step 7.2.3

Rewrite the expression.

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

Step 8

Cancel the common factor of $x - 2$ .

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Step 8.1

Cancel the common factor.

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

Step 8.2

Rewrite the expression.

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