Basic Math Examples

$\frac{a^{2} - 4 a - 21}{a^{2 - 6} a + 8} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 1

Factor $a^{2} - 4 a - 21$ 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 $- 21$ and whose sum is $- 4$ .

$- 7, 3$

Step 1.2

Write the factored form using these integers.

$\frac{(a - 7) (a + 3)}{a^{2 - 6} a + 8} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2

Simplify the denominator.

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Step 2.1

Multiply $a^{2 - 6}$ by $a$ by adding the exponents.

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Step 2.1.1

Multiply $a^{2 - 6}$ by $a$ .

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Step 2.1.1.1

Raise $a$ to the power of $1$ .

$\frac{(a - 7) (a + 3)}{a^{2 - 6} a^{1} + 8} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.1.1.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{(a - 7) (a + 3)}{a^{2 - 6 + 1} + 8} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.1.2

Subtract $6$ from $2$ .

$\frac{(a - 7) (a + 3)}{a^{- 4 + 1} + 8} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.1.3

Add $- 4$ and $1$ .

$\frac{(a - 7) (a + 3)}{a^{- 3} + 8} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.2

Rewrite $a^{- 3}$ as ${(a^{- 1})}^{3}$ .

$\frac{(a - 7) (a + 3)}{{(a^{- 1})}^{3} + 8} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.3

Rewrite $8$ as $2^{3}$ .

$\frac{(a - 7) (a + 3)}{{(a^{- 1})}^{3} + 2^{3}} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.4

Since both terms are perfect cubes, factor using the sum of cubes formula, $a^{3} + b^{3} = (a + b) (a^{2} - a b + b^{2})$ where $a = a^{- 1}$ and $b = 2$ .

$\frac{(a - 7) (a + 3)}{(a^{- 1} + 2) ({(a^{- 1})}^{2} - a^{- 1} \cdot 2 + 2^{2})} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5

Simplify.

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Step 2.5.1

Rewrite the expression using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$\frac{(a - 7) (a + 3)}{(\frac{1}{a} + 2) ({(a^{- 1})}^{2} - a^{- 1} \cdot 2 + 2^{2})} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.2

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

$\frac{(a - 7) (a + 3)}{(\frac{1}{a} + \frac{2 a}{a}) ({(a^{- 1})}^{2} - a^{- 1} \cdot 2 + 2^{2})} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.3

Combine the numerators over the common denominator.

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} ({(a^{- 1})}^{2} - a^{- 1} \cdot 2 + 2^{2})} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.4

Multiply the exponents in ${(a^{- 1})}^{2}$ .

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Step 2.5.4.1

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (a^{- 1 \cdot 2} - a^{- 1} \cdot 2 + 2^{2})} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.4.2

Multiply $- 1$ by $2$ .

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (a^{- 2} - a^{- 1} \cdot 2 + 2^{2})} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.5

Rewrite the expression using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1}{a^{2}} - a^{- 1} \cdot 2 + 2^{2})} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.6

Rewrite the expression using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1}{a^{2}} - \frac{1}{a} \cdot 2 + 2^{2})} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.7

Multiply $- \frac{1}{a} \cdot 2$ .

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Step 2.5.7.1

Multiply $2$ by $- 1$ .

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1}{a^{2}} - 2 \frac{1}{a} + 2^{2})} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.7.2

Combine $- 2$ and $\frac{1}{a}$ .

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1}{a^{2}} + \frac{- 2}{a} + 2^{2})} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.8

Move the negative in front of the fraction.

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1}{a^{2}} - \frac{2}{a} + 2^{2})} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.9

Raise $2$ to the power of $2$ .

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1}{a^{2}} - \frac{2}{a} + 4)} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.10

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

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1}{a^{2}} - \frac{2}{a} \cdot \frac{a}{a} + 4)} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.11

Write each expression with a common denominator of $a^{2}$ , by multiplying each by an appropriate factor of $1$ .

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Step 2.5.11.1

Multiply $\frac{2}{a}$ by $\frac{a}{a}$ .

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1}{a^{2}} - \frac{2 a}{a \cdot a} + 4)} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.11.2

Raise $a$ to the power of $1$ .

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1}{a^{2}} - \frac{2 a}{a^{1} a} + 4)} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.11.3

Raise $a$ to the power of $1$ .

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1}{a^{2}} - \frac{2 a}{a^{1} a^{1}} + 4)} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.11.4

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1}{a^{2}} - \frac{2 a}{a^{1 + 1}} + 4)} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.11.5

Add $1$ and $1$ .

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1}{a^{2}} - \frac{2 a}{a^{2}} + 4)} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.12

Combine the numerators over the common denominator.

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1 - 2 a}{a^{2}} + 4)} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.13

To write $4$ as a fraction with a common denominator, multiply by $\frac{a^{2}}{a^{2}}$ .

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} (\frac{1 - 2 a}{a^{2}} + \frac{4 a^{2}}{a^{2}})} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 2.5.14

Combine the numerators over the common denominator.

$\frac{(a - 7) (a + 3)}{\frac{1 + 2 a}{a} \cdot \frac{1 - 2 a + 4 a^{2}}{a^{2}}} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 3

Multiply $\frac{1 + 2 a}{a}$ by $\frac{1 - 2 a + 4 a^{2}}{a^{2}}$ .

$\frac{(a - 7) (a + 3)}{\frac{(1 + 2 a) (1 - 2 a + 4 a^{2})}{a \cdot a^{2}}} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 4

Multiply $a$ by $a^{2}$ by adding the exponents.

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Step 4.1

Multiply $a$ by $a^{2}$ .

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Step 4.1.1

Raise $a$ to the power of $1$ .

$\frac{(a - 7) (a + 3)}{\frac{(1 + 2 a) (1 - 2 a + 4 a^{2})}{a^{1} a^{2}}} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 4.1.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{(a - 7) (a + 3)}{\frac{(1 + 2 a) (1 - 2 a + 4 a^{2})}{a^{1 + 2}}} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 4.2

Add $1$ and $2$ .

$\frac{(a - 7) (a + 3)}{\frac{(1 + 2 a) (1 - 2 a + 4 a^{2})}{a^{3}}} \cdot \frac{a - 4}{a^{2} - 2 a - 35}$

Step 5

Factor $a^{2} - 2 a - 35$ using the AC method.

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Step 5.1

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 $- 35$ and whose sum is $- 2$ .

$- 7, 5$

Step 5.2

Write the factored form using these integers.

$\frac{(a - 7) (a + 3)}{\frac{(1 + 2 a) (1 - 2 a + 4 a^{2})}{a^{3}}} \cdot \frac{a - 4}{(a - 7) (a + 5)}$

Step 6

Simplify terms.

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Step 6.1

Cancel the common factor of $a - 7$ .

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Step 6.1.1

Cancel the common factor.

$\frac{(a - 7) (a + 3)}{\frac{(1 + 2 a) (1 - 2 a + 4 a^{2})}{a^{3}}} \cdot \frac{a - 4}{(a - 7) (a + 5)}$

Step 6.1.2

Rewrite the expression.

$\frac{a + 3}{\frac{(1 + 2 a) (1 - 2 a + 4 a^{2})}{a^{3}}} \cdot \frac{a - 4}{a + 5}$

Step 6.2

Multiply $\frac{a + 3}{\frac{(1 + 2 a) (1 - 2 a + 4 a^{2})}{a^{3}}}$ by $\frac{a - 4}{a + 5}$ .

$\frac{(a + 3) (a - 4)}{\frac{(1 + 2 a) (1 - 2 a + 4 a^{2})}{a^{3}} (a + 5)}$

Step 7

Factor $\frac{(1 + 2 a) (1 - 2 a + 4 a^{2})}{a^{3}}$ out of $\frac{(a + 3) (a - 4)}{\frac{(1 + 2 a) (1 - 2 a + 4 a^{2})}{a^{3}} (a + 5)}$ .

$\frac{a^{3}}{(1 + 2 a) (1 - 2 a + 4 a^{2})} \cdot \frac{(a + 3) (a - 4)}{a + 5}$

Step 8

Multiply $\frac{a^{3}}{(1 + 2 a) (1 - 2 a + 4 a^{2})}$ by $\frac{(a + 3) (a - 4)}{a + 5}$ .

$\frac{a^{3} (a + 3) (a - 4)}{(1 + 2 a) (1 - 2 a + 4 a^{2}) (a + 5)}$