Algebra Examples

$\frac{w^{2} - 81}{4 w^{2} + 27 w - 7} \div \frac{w^{2} - 5 w - 36}{w^{2} + 11 w + 28}$

Step 1

To divide by a fraction, multiply by its reciprocal.

$\frac{w^{2} - 81}{4 w^{2} + 27 w - 7} \cdot \frac{w^{2} + 11 w + 28}{w^{2} - 5 w - 36}$

Step 2

Simplify the numerator.

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Step 2.1

Rewrite $81$ as $9^{2}$ .

$\frac{w^{2} - 9^{2}}{4 w^{2} + 27 w - 7} \cdot \frac{w^{2} + 11 w + 28}{w^{2} - 5 w - 36}$

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 $a = w$ and $b = 9$ .

$\frac{(w + 9) (w - 9)}{4 w^{2} + 27 w - 7} \cdot \frac{w^{2} + 11 w + 28}{w^{2} - 5 w - 36}$

Step 3

Factor by grouping.

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Step 3.1

For a polynomial of the form $a x^{2} + b x + c$ , rewrite the middle term as a sum of two terms whose product is $a \cdot c = 4 \cdot - 7 = - 28$ and whose sum is $b = 27$ .

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Step 3.1.1

Factor $27$ out of $27 w$ .

$\frac{(w + 9) (w - 9)}{4 w^{2} + 27 (w) - 7} \cdot \frac{w^{2} + 11 w + 28}{w^{2} - 5 w - 36}$

Step 3.1.2

Rewrite $27$ as $- 1$ plus $28$

$\frac{(w + 9) (w - 9)}{4 w^{2} + (- 1 + 28) w - 7} \cdot \frac{w^{2} + 11 w + 28}{w^{2} - 5 w - 36}$

Step 3.1.3

Apply the distributive property.

$\frac{(w + 9) (w - 9)}{4 w^{2} - 1 w + 28 w - 7} \cdot \frac{w^{2} + 11 w + 28}{w^{2} - 5 w - 36}$

Step 3.2

Factor out the greatest common factor from each group.

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Step 3.2.1

Group the first two terms and the last two terms.

$\frac{(w + 9) (w - 9)}{(4 w^{2} - 1 w) + 28 w - 7} \cdot \frac{w^{2} + 11 w + 28}{w^{2} - 5 w - 36}$

Step 3.2.2

Factor out the greatest common factor (GCF) from each group.

$\frac{(w + 9) (w - 9)}{w (4 w - 1) + 7 (4 w - 1)} \cdot \frac{w^{2} + 11 w + 28}{w^{2} - 5 w - 36}$

Step 3.3

Factor the polynomial by factoring out the greatest common factor, $4 w - 1$ .

$\frac{(w + 9) (w - 9)}{(4 w - 1) (w + 7)} \cdot \frac{w^{2} + 11 w + 28}{w^{2} - 5 w - 36}$

Step 4

Factor $w^{2} + 11 w + 28$ using the AC method.

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Step 4.1

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 $28$ and whose sum is $11$ .

$4, 7$

Step 4.2

Write the factored form using these integers.

$\frac{(w + 9) (w - 9)}{(4 w - 1) (w + 7)} \cdot \frac{(w + 4) (w + 7)}{w^{2} - 5 w - 36}$

Step 5

Factor $w^{2} - 5 w - 36$ 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 $- 36$ and whose sum is $- 5$ .

$- 9, 4$

Step 5.2

Write the factored form using these integers.

$\frac{(w + 9) (w - 9)}{(4 w - 1) (w + 7)} \cdot \frac{(w + 4) (w + 7)}{(w - 9) (w + 4)}$

Step 6

Simplify terms.

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Step 6.1

Cancel the common factor of $w - 9$ .

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Step 6.1.1

Factor $w - 9$ out of $(w + 9) (w - 9)$ .

$\frac{(w - 9) (w + 9)}{(4 w - 1) (w + 7)} \cdot \frac{(w + 4) (w + 7)}{(w - 9) (w + 4)}$

Step 6.1.2

Cancel the common factor.

$\frac{(w - 9) (w + 9)}{(4 w - 1) (w + 7)} \cdot \frac{(w + 4) (w + 7)}{(w - 9) (w + 4)}$

Step 6.1.3

Rewrite the expression.

$\frac{w + 9}{(4 w - 1) (w + 7)} \cdot \frac{(w + 4) (w + 7)}{w + 4}$

Step 6.2

Cancel the common factor of $w + 7$ .

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Step 6.2.1

Factor $w + 7$ out of $(4 w - 1) (w + 7)$ .

$\frac{w + 9}{(w + 7) (4 w - 1)} \cdot \frac{(w + 4) (w + 7)}{w + 4}$

Step 6.2.2

Factor $w + 7$ out of $(w + 4) (w + 7)$ .

$\frac{w + 9}{(w + 7) (4 w - 1)} \cdot \frac{(w + 7) (w + 4)}{w + 4}$

Step 6.2.3

Cancel the common factor.

$\frac{w + 9}{(w + 7) (4 w - 1)} \cdot \frac{(w + 7) (w + 4)}{w + 4}$

Step 6.2.4

Rewrite the expression.

$\frac{w + 9}{4 w - 1} \cdot \frac{w + 4}{w + 4}$

Step 6.3

Multiply $\frac{w + 9}{4 w - 1}$ by $\frac{w + 4}{w + 4}$ .

$\frac{(w + 9) (w + 4)}{(4 w - 1) (w + 4)}$

Step 6.4

Cancel the common factor of $w + 4$ .

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Step 6.4.1

Cancel the common factor.

$\frac{(w + 9) (w + 4)}{(4 w - 1) (w + 4)}$

Step 6.4.2

Rewrite the expression.

$\frac{w + 9}{4 w - 1}$