Pre-Algebra Examples

$\frac{11}{x + 4} - \frac{x - 6}{x - 10} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1

Simplify $\frac{11}{x + 4} - \frac{x - 6}{x - 10}$ .

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Step 1.1

To write $\frac{11}{x + 4}$ as a fraction with a common denominator, multiply by $\frac{x - 10}{x - 10}$ .

$\frac{11}{x + 4} \cdot \frac{x - 10}{x - 10} - \frac{x - 6}{x - 10} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.2

To write $- \frac{x - 6}{x - 10}$ as a fraction with a common denominator, multiply by $\frac{x + 4}{x + 4}$ .

$\frac{11}{x + 4} \cdot \frac{x - 10}{x - 10} - \frac{x - 6}{x - 10} \cdot \frac{x + 4}{x + 4} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.3

Write each expression with a common denominator of $(x + 4) (x - 10)$ , by multiplying each by an appropriate factor of $1$ .

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Step 1.3.1

Multiply $\frac{11}{x + 4}$ by $\frac{x - 10}{x - 10}$ .

$\frac{11 (x - 10)}{(x + 4) (x - 10)} - \frac{x - 6}{x - 10} \cdot \frac{x + 4}{x + 4} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.3.2

Multiply $\frac{x - 6}{x - 10}$ by $\frac{x + 4}{x + 4}$ .

$\frac{11 (x - 10)}{(x + 4) (x - 10)} - \frac{(x - 6) (x + 4)}{(x - 10) (x + 4)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.3.3

Reorder the factors of $(x - 10) (x + 4)$ .

$\frac{11 (x - 10)}{(x + 4) (x - 10)} - \frac{(x - 6) (x + 4)}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.4

Combine the numerators over the common denominator.

$\frac{11 (x - 10) - (x - 6) (x + 4)}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5

Simplify the numerator.

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Step 1.5.1

Apply the distributive property.

$\frac{11 x + 11 \cdot - 10 - (x - 6) (x + 4)}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.2

Multiply $11$ by $- 10$ .

$\frac{11 x - 110 - (x - 6) (x + 4)}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.3

Apply the distributive property.

$\frac{11 x - 110 + (- x - - 6) (x + 4)}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.4

Multiply $- 1$ by $- 6$ .

$\frac{11 x - 110 + (- x + 6) (x + 4)}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.5

Expand $(- x + 6) (x + 4)$ using the FOIL Method.

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Step 1.5.5.1

Apply the distributive property.

$\frac{11 x - 110 - x (x + 4) + 6 (x + 4)}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.5.2

Apply the distributive property.

$\frac{11 x - 110 - x \cdot x - x \cdot 4 + 6 (x + 4)}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.5.3

Apply the distributive property.

$\frac{11 x - 110 - x \cdot x - x \cdot 4 + 6 x + 6 \cdot 4}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.6

Simplify and combine like terms.

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Step 1.5.6.1

Simplify each term.

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Step 1.5.6.1.1

Multiply $x$ by $x$ by adding the exponents.

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Step 1.5.6.1.1.1

Move $x$ .

$\frac{11 x - 110 - (x \cdot x) - x \cdot 4 + 6 x + 6 \cdot 4}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.6.1.1.2

Multiply $x$ by $x$ .

$\frac{11 x - 110 - x^{2} - x \cdot 4 + 6 x + 6 \cdot 4}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.6.1.2

Multiply $4$ by $- 1$ .

$\frac{11 x - 110 - x^{2} - 4 x + 6 x + 6 \cdot 4}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.6.1.3

Multiply $6$ by $4$ .

$\frac{11 x - 110 - x^{2} - 4 x + 6 x + 24}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.6.2

Add $- 4 x$ and $6 x$ .

$\frac{11 x - 110 - x^{2} + 2 x + 24}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.7

Add $11 x$ and $2 x$ .

$\frac{13 x - 110 - x^{2} + 24}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.8

Add $- 110$ and $24$ .

$\frac{13 x - x^{2} - 86}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.5.9

Reorder terms.

$\frac{- x^{2} + 13 x - 86}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.6

Simplify with factoring out.

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Step 1.6.1

Factor $- 1$ out of $- x^{2}$ .

$\frac{- (x^{2}) + 13 x - 86}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.6.2

Factor $- 1$ out of $13 x$ .

$\frac{- (x^{2}) - (- 13 x) - 86}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.6.3

Factor $- 1$ out of $- (x^{2}) - (- 13 x)$ .

$\frac{- (x^{2} - 13 x) - 86}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.6.4

Rewrite $- 86$ as $- 1 (86)$ .

$\frac{- (x^{2} - 13 x) - 1 (86)}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.6.5

Factor $- 1$ out of $- (x^{2} - 13 x) - 1 (86)$ .

$\frac{- (x^{2} - 13 x + 86)}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.6.6

Simplify the expression.

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Step 1.6.6.1

Rewrite $- (x^{2} - 13 x + 86)$ as $- 1 (x^{2} - 13 x + 86)$ .

$\frac{- 1 (x^{2} - 13 x + 86)}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 1.6.6.2

Move the negative in front of the fraction.

$- \frac{x^{2} - 13 x + 86}{(x + 4) (x - 10)} = \frac{- x^{2}}{x^{2} - 6 x - 40}$

Step 2

Simplify $\frac{- x^{2}}{x^{2} - 6 x - 40}$ .

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Step 2.1

Factor $x^{2} - 6 x - 40$ using the AC method.

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Step 2.1.1

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 $- 40$ and whose sum is $- 6$ .

$- 10, 4$

Step 2.1.2

Write the factored form using these integers.

$- \frac{x^{2} - 13 x + 86}{(x + 4) (x - 10)} = \frac{- x^{2}}{(x - 10) (x + 4)}$

Step 2.2

Move the negative in front of the fraction.

$- \frac{x^{2} - 13 x + 86}{(x + 4) (x - 10)} = - \frac{x^{2}}{(x - 10) (x + 4)}$

Step 3

Graph each side of the equation. The solution is the x-value of the point of intersection.

$x \approx 6.61538461$

Step 4