Pre-Algebra Examples

$\frac{3 x - x^{2}}{x^{2} - 9}$

Step 1

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

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Step 1.1

Factor $x$ out of $3 x$ .

$\frac{x \cdot 3 - x^{2}}{x^{2} - 9}$

Step 1.2

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

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

Step 1.3

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

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

Step 2

Simplify the denominator.

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Step 2.1

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

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

Step 2.2

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 $b = 3$ .

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

Step 3

Reduce the expression by cancelling the common factors.

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Step 3.1

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

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Step 3.1.1

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

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

Step 3.1.2

Factor $- 1$ out of $- x$ .

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

Step 3.1.3

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

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

Step 3.1.4

Reorder terms.

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

Step 3.1.5

Cancel the common factor.

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

Step 3.1.6

Rewrite the expression.

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

Step 3.2

Simplify the expression.

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Step 3.2.1

Move $- 1$ to the left of $x$ .

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

Step 3.2.2

Move the negative in front of the fraction.

$- \frac{x}{x + 3}$