Algebra Examples

$\frac{x + 6}{x^{2} + 8 x + 15} + \frac{3 x}{x + 5} - \frac{x - 3}{x + 3}$

Step 1

Factor $x^{2} + 8 x + 15$ using the AC method.

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Step 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 $15$ and whose sum is $8$ .

$3, 5$

Step 1.2

Write the factored form using these integers.

$\frac{x + 6}{(x + 3) (x + 5)} + \frac{3 x}{x + 5} - \frac{x - 3}{x + 3}$

Step 2

Find the common denominator.

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Step 2.1

Multiply $\frac{3 x}{x + 5}$ by $\frac{x + 3}{x + 3}$ .

$\frac{x + 6}{(x + 3) (x + 5)} + \frac{3 x}{x + 5} \cdot \frac{x + 3}{x + 3} - \frac{x - 3}{x + 3}$

Step 2.2

Multiply $\frac{3 x}{x + 5}$ by $\frac{x + 3}{x + 3}$ .

$\frac{x + 6}{(x + 3) (x + 5)} + \frac{3 x (x + 3)}{(x + 5) (x + 3)} - \frac{x - 3}{x + 3}$

Step 2.3

Multiply $\frac{x - 3}{x + 3}$ by $\frac{x + 5}{x + 5}$ .

$\frac{x + 6}{(x + 3) (x + 5)} + \frac{3 x (x + 3)}{(x + 5) (x + 3)} - (\frac{x - 3}{x + 3} \cdot \frac{x + 5}{x + 5})$

Step 2.4

Multiply $\frac{x - 3}{x + 3}$ by $\frac{x + 5}{x + 5}$ .

$\frac{x + 6}{(x + 3) (x + 5)} + \frac{3 x (x + 3)}{(x + 5) (x + 3)} - \frac{(x - 3) (x + 5)}{(x + 3) (x + 5)}$

Step 2.5

Reorder the factors of $(x + 5) (x + 3)$ .

$\frac{x + 6}{(x + 3) (x + 5)} + \frac{3 x (x + 3)}{(x + 3) (x + 5)} - \frac{(x - 3) (x + 5)}{(x + 3) (x + 5)}$

Step 3

Combine the numerators over the common denominator.

$\frac{x + 6 + 3 x (x + 3) - (x - 3) (x + 5)}{(x + 3) (x + 5)}$

Step 4

Simplify each term.

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Step 4.1

Apply the distributive property.

$\frac{x + 6 + 3 x \cdot x + 3 x \cdot 3 - (x - 3) (x + 5)}{(x + 3) (x + 5)}$

Step 4.2

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

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Step 4.2.1

Move $x$ .

$\frac{x + 6 + 3 (x \cdot x) + 3 x \cdot 3 - (x - 3) (x + 5)}{(x + 3) (x + 5)}$

Step 4.2.2

Multiply $x$ by $x$ .

$\frac{x + 6 + 3 x^{2} + 3 x \cdot 3 - (x - 3) (x + 5)}{(x + 3) (x + 5)}$

Step 4.3

Multiply $3$ by $3$ .

$\frac{x + 6 + 3 x^{2} + 9 x - (x - 3) (x + 5)}{(x + 3) (x + 5)}$

Step 4.4

Apply the distributive property.

$\frac{x + 6 + 3 x^{2} + 9 x + (- x - - 3) (x + 5)}{(x + 3) (x + 5)}$

Step 4.5

Multiply $- 1$ by $- 3$ .

$\frac{x + 6 + 3 x^{2} + 9 x + (- x + 3) (x + 5)}{(x + 3) (x + 5)}$

Step 4.6

Expand $(- x + 3) (x + 5)$ using the FOIL Method.

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Step 4.6.1

Apply the distributive property.

$\frac{x + 6 + 3 x^{2} + 9 x - x (x + 5) + 3 (x + 5)}{(x + 3) (x + 5)}$

Step 4.6.2

Apply the distributive property.

$\frac{x + 6 + 3 x^{2} + 9 x - x \cdot x - x \cdot 5 + 3 (x + 5)}{(x + 3) (x + 5)}$

Step 4.6.3

Apply the distributive property.

$\frac{x + 6 + 3 x^{2} + 9 x - x \cdot x - x \cdot 5 + 3 x + 3 \cdot 5}{(x + 3) (x + 5)}$

Step 4.7

Simplify and combine like terms.

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Step 4.7.1

Simplify each term.

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Step 4.7.1.1

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

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Step 4.7.1.1.1

Move $x$ .

$\frac{x + 6 + 3 x^{2} + 9 x - (x \cdot x) - x \cdot 5 + 3 x + 3 \cdot 5}{(x + 3) (x + 5)}$

Step 4.7.1.1.2

Multiply $x$ by $x$ .

$\frac{x + 6 + 3 x^{2} + 9 x - x^{2} - x \cdot 5 + 3 x + 3 \cdot 5}{(x + 3) (x + 5)}$

Step 4.7.1.2

Multiply $5$ by $- 1$ .

$\frac{x + 6 + 3 x^{2} + 9 x - x^{2} - 5 x + 3 x + 3 \cdot 5}{(x + 3) (x + 5)}$

Step 4.7.1.3

Multiply $3$ by $5$ .

$\frac{x + 6 + 3 x^{2} + 9 x - x^{2} - 5 x + 3 x + 15}{(x + 3) (x + 5)}$

Step 4.7.2

Add $- 5 x$ and $3 x$ .

$\frac{x + 6 + 3 x^{2} + 9 x - x^{2} - 2 x + 15}{(x + 3) (x + 5)}$

Step 5

Simplify by adding terms.

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Step 5.1

Add $x$ and $9 x$ .

$\frac{10 x + 6 + 3 x^{2} - x^{2} - 2 x + 15}{(x + 3) (x + 5)}$

Step 5.2

Subtract $2 x$ from $10 x$ .

$\frac{6 + 3 x^{2} - x^{2} + 8 x + 15}{(x + 3) (x + 5)}$

Step 5.3

Add $6$ and $15$ .

$\frac{3 x^{2} - x^{2} + 8 x + 21}{(x + 3) (x + 5)}$

Step 5.4

Subtract $x^{2}$ from $3 x^{2}$ .

$\frac{2 x^{2} + 8 x + 21}{(x + 3) (x + 5)}$