Precalculus Examples

$(\frac{x^{2} + 2 x y + y^{2}}{x^{2} - y^{2}}) (\frac{5 x^{2} - x y - 4 y^{2}}{4 x^{2} - x y - 5 y^{2}})$

Step 1

Factor using the perfect square rule.

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Step 1.1

Check that the middle term is two times the product of the numbers being squared in the first term and third term.

$2 x y = 2 \cdot x \cdot y$

Step 1.2

Rewrite the polynomial.

$\frac{x^{2} + 2 \cdot x \cdot y + y^{2}}{x^{2} - y^{2}} \cdot \frac{5 x^{2} - x y - 4 y^{2}}{4 x^{2} - x y - 5 y^{2}}$

Step 1.3

Factor using the perfect square trinomial rule $a^{2} + 2 a b + b^{2} = {(a + b)}^{2}$ , where $a = x$ and $b = y$ .

$\frac{{(x + y)}^{2}}{x^{2} - y^{2}} \cdot \frac{5 x^{2} - x y - 4 y^{2}}{4 x^{2} - x y - 5 y^{2}}$

Step 2

Since both terms are perfect squares, factor using the difference of squares formula, $a^{2} - b^{2} = (a + b) (a - b)$ where $a = x$ and $b = y$ .

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{5 x^{2} - x y - 4 y^{2}}{4 x^{2} - x y - 5 y^{2}}$

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 $a \cdot c = 5 \cdot - 4 = - 20$ and whose sum is $b = - 1$ .

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Step 3.1.1

Reorder terms.

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{5 x^{2} - 4 y^{2} - x y}{4 x^{2} - x y - 5 y^{2}}$

Step 3.1.2

Reorder $- 4 y^{2}$ and $- x y$ .

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{5 x^{2} - x y - 4 y^{2}}{4 x^{2} - x y - 5 y^{2}}$

Step 3.1.3

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

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{5 x^{2} - (x y) - 4 y^{2}}{4 x^{2} - x y - 5 y^{2}}$

Step 3.1.4

Rewrite $- 1$ as $4$ plus $- 5$

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{5 x^{2} + (4 - 5) (x y) - 4 y^{2}}{4 x^{2} - x y - 5 y^{2}}$

Step 3.1.5

Apply the distributive property.

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{5 x^{2} + 4 (x y) - 5 (x y) - 4 y^{2}}{4 x^{2} - x y - 5 y^{2}}$

Step 3.1.6

Move parentheses.

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{5 x^{2} + 4 x y - 5 x y - 4 y^{2}}{4 x^{2} - x y - 5 y^{2}}$

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.

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{(5 x^{2} + 4 x y) - 5 x y - 4 y^{2}}{4 x^{2} - x y - 5 y^{2}}$

Step 3.2.2

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

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{x (5 x + 4 y) - y (5 x + 4 y)}{4 x^{2} - x y - 5 y^{2}}$

Step 3.3

Factor the polynomial by factoring out the greatest common factor, $5 x + 4 y$ .

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{(5 x + 4 y) (x - y)}{4 x^{2} - x y - 5 y^{2}}$

Step 4

Factor by grouping.

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Step 4.1

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 $a \cdot c = 4 \cdot - 5 = - 20$ and whose sum is $b = - 1$ .

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Step 4.1.1

Reorder terms.

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{(5 x + 4 y) (x - y)}{4 x^{2} - 5 y^{2} - x y}$

Step 4.1.2

Reorder $- 5 y^{2}$ and $- x y$ .

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{(5 x + 4 y) (x - y)}{4 x^{2} - x y - 5 y^{2}}$

Step 4.1.3

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

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{(5 x + 4 y) (x - y)}{4 x^{2} - (x y) - 5 y^{2}}$

Step 4.1.4

Rewrite $- 1$ as $4$ plus $- 5$

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{(5 x + 4 y) (x - y)}{4 x^{2} + (4 - 5) (x y) - 5 y^{2}}$

Step 4.1.5

Apply the distributive property.

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{(5 x + 4 y) (x - y)}{4 x^{2} + 4 (x y) - 5 (x y) - 5 y^{2}}$

Step 4.1.6

Move parentheses.

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{(5 x + 4 y) (x - y)}{4 x^{2} + 4 x y - 5 x y - 5 y^{2}}$

Step 4.2

Factor out the greatest common factor from each group.

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Step 4.2.1

Group the first two terms and the last two terms.

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{(5 x + 4 y) (x - y)}{(4 x^{2} + 4 x y) - 5 x y - 5 y^{2}}$

Step 4.2.2

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

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{(5 x + 4 y) (x - y)}{4 x (x + y) - 5 y (x + y)}$

Step 4.3

Factor the polynomial by factoring out the greatest common factor, $x + y$ .

$\frac{{(x + y)}^{2}}{(x + y) (x - y)} \cdot \frac{(5 x + 4 y) (x - y)}{(x + y) (4 x - 5 y)}$

Step 5

Combine.

$\frac{{(x + y)}^{2} ((5 x + 4 y) (x - y))}{(x + y) (x - y) ((x + y) (4 x - 5 y))}$

Step 6

Cancel the common factor of ${(x + y)}^{2}$ and $x + y$ .

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Step 6.1

Factor $x + y$ out of ${(x + y)}^{2} ((5 x + 4 y) (x - y))$ .

$\frac{(x + y) ((x + y) ((5 x + 4 y) (x - y)))}{(x + y) (x - y) ((x + y) (4 x - 5 y))}$

Step 6.2

Cancel the common factors.

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Step 6.2.1

Factor $x + y$ out of $(x + y) (x - y) ((x + y) (4 x - 5 y))$ .

$\frac{(x + y) ((x + y) ((5 x + 4 y) (x - y)))}{(x + y) ((x - y) ((x + y) (4 x - 5 y)))}$

Step 6.2.2

Cancel the common factor.

$\frac{(x + y) ((x + y) ((5 x + 4 y) (x - y)))}{(x + y) ((x - y) ((x + y) (4 x - 5 y)))}$

Step 6.2.3

Rewrite the expression.

$\frac{(x + y) ((5 x + 4 y) (x - y))}{(x - y) ((x + y) (4 x - 5 y))}$

Step 7

Cancel the common factor of $x + y$ .

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Step 7.1

Cancel the common factor.

$\frac{(x + y) ((5 x + 4 y) (x - y))}{(x - y) ((x + y) (4 x - 5 y))}$

Step 7.2

Rewrite the expression.

$\frac{(5 x + 4 y) (x - y)}{(x - y) (4 x - 5 y)}$

Step 8

Cancel the common factor of $x - y$ .

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Step 8.1

Cancel the common factor.

$\frac{(5 x + 4 y) (x - y)}{(x - y) (4 x - 5 y)}$

Step 8.2

Rewrite the expression.

$\frac{5 x + 4 y}{4 x - 5 y}$