Algebra Examples

$\frac{8 x^{3} - 125 y^{3}}{{(2 x + 5 y)}^{3}} \div \frac{4 x^{2} + 10 x y + 25 y^{2}}{4 x^{2} + 20 x y + 25 y^{2}}$

Step 1

To divide by a fraction, multiply by its reciprocal.

$\frac{8 x^{3} - 125 y^{3}}{{(2 x + 5 y)}^{3}} \cdot \frac{4 x^{2} + 20 x y + 25 y^{2}}{4 x^{2} + 10 x y + 25 y^{2}}$

Step 2

Simplify the numerator.

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Step 2.1

Rewrite $8 x^{3}$ as ${(2 x)}^{3}$ .

$\frac{{(2 x)}^{3} - 125 y^{3}}{{(2 x + 5 y)}^{3}} \cdot \frac{4 x^{2} + 20 x y + 25 y^{2}}{4 x^{2} + 10 x y + 25 y^{2}}$

Step 2.2

Rewrite $125 y^{3}$ as ${(5 y)}^{3}$ .

$\frac{{(2 x)}^{3} - {(5 y)}^{3}}{{(2 x + 5 y)}^{3}} \cdot \frac{4 x^{2} + 20 x y + 25 y^{2}}{4 x^{2} + 10 x y + 25 y^{2}}$

Step 2.3

Since both terms are perfect cubes, factor using the difference of cubes formula, $a^{3} - b^{3} = (a - b) (a^{2} + a b + b^{2})$ where $a = 2 x$ and $b = 5 y$ .

$\frac{(2 x - (5 y)) ({(2 x)}^{2} + 2 x (5 y) + {(5 y)}^{2})}{{(2 x + 5 y)}^{3}} \cdot \frac{4 x^{2} + 20 x y + 25 y^{2}}{4 x^{2} + 10 x y + 25 y^{2}}$

Step 2.4

Simplify.

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Step 2.4.1

Multiply $5$ by $- 1$ .

$\frac{(2 x - 5 y) ({(2 x)}^{2} + 2 x (5 y) + {(5 y)}^{2})}{{(2 x + 5 y)}^{3}} \cdot \frac{4 x^{2} + 20 x y + 25 y^{2}}{4 x^{2} + 10 x y + 25 y^{2}}$

Step 2.4.2

Apply the product rule to $2 x$ .

$\frac{(2 x - 5 y) (2^{2} x^{2} + 2 x (5 y) + {(5 y)}^{2})}{{(2 x + 5 y)}^{3}} \cdot \frac{4 x^{2} + 20 x y + 25 y^{2}}{4 x^{2} + 10 x y + 25 y^{2}}$

Step 2.4.3

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

$\frac{(2 x - 5 y) (4 x^{2} + 2 x (5 y) + {(5 y)}^{2})}{{(2 x + 5 y)}^{3}} \cdot \frac{4 x^{2} + 20 x y + 25 y^{2}}{4 x^{2} + 10 x y + 25 y^{2}}$

Step 2.4.4

Rewrite using the commutative property of multiplication.

$\frac{(2 x - 5 y) (4 x^{2} + 2 \cdot 5 x y + {(5 y)}^{2})}{{(2 x + 5 y)}^{3}} \cdot \frac{4 x^{2} + 20 x y + 25 y^{2}}{4 x^{2} + 10 x y + 25 y^{2}}$

Step 2.4.5

Multiply $2$ by $5$ .

$\frac{(2 x - 5 y) (4 x^{2} + 10 x y + {(5 y)}^{2})}{{(2 x + 5 y)}^{3}} \cdot \frac{4 x^{2} + 20 x y + 25 y^{2}}{4 x^{2} + 10 x y + 25 y^{2}}$

Step 2.4.6

Apply the product rule to $5 y$ .

$\frac{(2 x - 5 y) (4 x^{2} + 10 x y + 5^{2} y^{2})}{{(2 x + 5 y)}^{3}} \cdot \frac{4 x^{2} + 20 x y + 25 y^{2}}{4 x^{2} + 10 x y + 25 y^{2}}$

Step 2.4.7

Raise $5$ to the power of $2$ .

$\frac{(2 x - 5 y) (4 x^{2} + 10 x y + 25 y^{2})}{{(2 x + 5 y)}^{3}} \cdot \frac{4 x^{2} + 20 x y + 25 y^{2}}{4 x^{2} + 10 x y + 25 y^{2}}$

Step 3

Simplify terms.

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Step 3.1

Cancel the common factor of $4 x^{2} + 10 x y + 25 y^{2}$ .

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Step 3.1.1

Factor $4 x^{2} + 10 x y + 25 y^{2}$ out of $(2 x - 5 y) (4 x^{2} + 10 x y + 25 y^{2})$ .

$\frac{(4 x^{2} + 10 x y + 25 y^{2}) (2 x - 5 y)}{{(2 x + 5 y)}^{3}} \cdot \frac{4 x^{2} + 20 x y + 25 y^{2}}{4 x^{2} + 10 x y + 25 y^{2}}$

Step 3.1.2

Cancel the common factor.

$\frac{(4 x^{2} + 10 x y + 25 y^{2}) (2 x - 5 y)}{{(2 x + 5 y)}^{3}} \cdot \frac{4 x^{2} + 20 x y + 25 y^{2}}{4 x^{2} + 10 x y + 25 y^{2}}$

Step 3.1.3

Rewrite the expression.

$\frac{2 x - 5 y}{{(2 x + 5 y)}^{3}} (4 x^{2} + 20 x y + 25 y^{2})$

Step 3.2

Multiply $\frac{2 x - 5 y}{{(2 x + 5 y)}^{3}}$ by $4 x^{2} + 20 x y + 25 y^{2}$ .

$\frac{(2 x - 5 y) (4 x^{2} + 20 x y + 25 y^{2})}{{(2 x + 5 y)}^{3}}$

Step 4

Factor using the perfect square rule.

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Step 4.1

Rewrite $4 x^{2}$ as ${(2 x)}^{2}$ .

$\frac{(2 x - 5 y) ({(2 x)}^{2} + 20 x y + 25 y^{2})}{{(2 x + 5 y)}^{3}}$

Step 4.2

Rewrite $25 y^{2}$ as ${(5 y)}^{2}$ .

$\frac{(2 x - 5 y) ({(2 x)}^{2} + 20 x y + {(5 y)}^{2})}{{(2 x + 5 y)}^{3}}$

Step 4.3

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

$20 x y = 2 \cdot (2 x) \cdot (5 y)$

Step 4.4

Rewrite the polynomial.

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

Step 4.5

Factor using the perfect square trinomial rule $a^{2} + 2 a b + b^{2} = {(a + b)}^{2}$ , where $a = 2 x$ and $b = 5 y$ .

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

Step 5

Cancel the common factor of ${(2 x + 5 y)}^{2}$ and ${(2 x + 5 y)}^{3}$ .

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Step 5.1

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

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

Step 5.2

Cancel the common factors.

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Step 5.2.1

Factor ${(2 x + 5 y)}^{2}$ out of ${(2 x + 5 y)}^{3}$ .

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

Step 5.2.2

Cancel the common factor.

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

Step 5.2.3

Rewrite the expression.

$\frac{2 x - 5 y}{2 x + 5 y}$