Pre-Algebra Examples

$(\frac{2}{x + 2} + \frac{10}{x + 5}) \div \frac{7 x + 20}{x^{2} + 7 x + 10}$

Step 1

To divide by a fraction, multiply by its reciprocal.

$(\frac{2}{x + 2} + \frac{10}{x + 5}) \frac{x^{2} + 7 x + 10}{7 x + 20}$

Step 2

Factor $x^{2} + 7 x + 10$ 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 $10$ and whose sum is $7$ .

$2, 5$

Step 2.2

Write the factored form using these integers.

$(\frac{2}{x + 2} + \frac{10}{x + 5}) \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 3

To write $\frac{2}{x + 2}$ as a fraction with a common denominator, multiply by $\frac{x + 5}{x + 5}$ .

$(\frac{2}{x + 2} \cdot \frac{x + 5}{x + 5} + \frac{10}{x + 5}) \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 4

To write $\frac{10}{x + 5}$ as a fraction with a common denominator, multiply by $\frac{x + 2}{x + 2}$ .

$(\frac{2}{x + 2} \cdot \frac{x + 5}{x + 5} + \frac{10}{x + 5} \cdot \frac{x + 2}{x + 2}) \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 5

Write each expression with a common denominator of $(x + 2) (x + 5)$ , by multiplying each by an appropriate factor of $1$ .

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Step 5.1

Multiply $\frac{2}{x + 2}$ by $\frac{x + 5}{x + 5}$ .

$(\frac{2 (x + 5)}{(x + 2) (x + 5)} + \frac{10}{x + 5} \cdot \frac{x + 2}{x + 2}) \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 5.2

Multiply $\frac{10}{x + 5}$ by $\frac{x + 2}{x + 2}$ .

$(\frac{2 (x + 5)}{(x + 2) (x + 5)} + \frac{10 (x + 2)}{(x + 5) (x + 2)}) \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 5.3

Reorder the factors of $(x + 5) (x + 2)$ .

$(\frac{2 (x + 5)}{(x + 2) (x + 5)} + \frac{10 (x + 2)}{(x + 2) (x + 5)}) \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 6

Combine the numerators over the common denominator.

$\frac{2 (x + 5) + 10 (x + 2)}{(x + 2) (x + 5)} \cdot \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 7

Simplify the numerator.

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Step 7.1

Factor $2$ out of $2 (x + 5) + 10 (x + 2)$ .

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Step 7.1.1

Factor $2$ out of $10 (x + 2)$ .

$\frac{2 (x + 5) + 2 (5 (x + 2))}{(x + 2) (x + 5)} \cdot \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 7.1.2

Factor $2$ out of $2 (x + 5) + 2 (5 (x + 2))$ .

$\frac{2 (x + 5 + 5 (x + 2))}{(x + 2) (x + 5)} \cdot \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 7.2

Apply the distributive property.

$\frac{2 (x + 5 + 5 x + 5 \cdot 2)}{(x + 2) (x + 5)} \cdot \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 7.3

Multiply $5$ by $2$ .

$\frac{2 (x + 5 + 5 x + 10)}{(x + 2) (x + 5)} \cdot \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 7.4

Add $x$ and $5 x$ .

$\frac{2 (6 x + 5 + 10)}{(x + 2) (x + 5)} \cdot \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 7.5

Add $5$ and $10$ .

$\frac{2 (6 x + 15)}{(x + 2) (x + 5)} \cdot \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 7.6

Factor $3$ out of $6 x + 15$ .

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Step 7.6.1

Factor $3$ out of $6 x$ .

$\frac{2 (3 (2 x) + 15)}{(x + 2) (x + 5)} \cdot \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 7.6.2

Factor $3$ out of $15$ .

$\frac{2 (3 (2 x) + 3 (5))}{(x + 2) (x + 5)} \cdot \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 7.6.3

Factor $3$ out of $3 (2 x) + 3 (5)$ .

$\frac{2 (3 (2 x + 5))}{(x + 2) (x + 5)} \cdot \frac{(x + 2) (x + 5)}{7 x + 20}$

$\frac{2 \cdot 3 (2 x + 5)}{(x + 2) (x + 5)} \cdot \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 7.7

Multiply $2$ by $3$ .

$\frac{6 (2 x + 5)}{(x + 2) (x + 5)} \cdot \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 8

Cancel the common factor of $(x + 2) (x + 5)$ .

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Step 8.1

Cancel the common factor.

$\frac{6 (2 x + 5)}{(x + 2) (x + 5)} \cdot \frac{(x + 2) (x + 5)}{7 x + 20}$

Step 8.2

Rewrite the expression.

$6 (2 x + 5) \frac{1}{7 x + 20}$

Step 9

Combine $\frac{1}{7 x + 20}$ and $6$ .

$\frac{6}{7 x + 20} (2 x + 5)$

Step 10

Multiply $\frac{6}{7 x + 20}$ by $2 x + 5$ .

$\frac{6 (2 x + 5)}{7 x + 20}$