Pre-Algebra Examples

$\frac{y - 4}{y^{2} - 9 y + 18} \cdot \frac{y^{2} + y - 12}{y + 4} \div \frac{y^{2} - 16}{y^{2} + 10 y + 24}$

Step 1

Factor $y^{2} - 9 y + 18$ 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 $18$ and whose sum is $- 9$ .

$- 6, - 3$

Step 1.2

Write the factored form using these integers.

$\frac{y - 4}{(y - 6) (y - 3)} \cdot \frac{y^{2} + y - 12}{y + 4} \div \frac{y^{2} - 16}{y^{2} + 10 y + 24}$

Step 2

Factor $y^{2} + y - 12$ using the AC method.

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Step 2.1

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 $- 12$ and whose sum is $1$ .

$- 3, 4$

Step 2.2

Write the factored form using these integers.

$\frac{y - 4}{(y - 6) (y - 3)} \cdot \frac{(y - 3) (y + 4)}{y + 4} \div \frac{y^{2} - 16}{y^{2} + 10 y + 24}$

Step 3

Reduce the expression by cancelling the common factors.

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Step 3.1

Reduce the expression $\frac{(y - 3) (y + 4)}{y + 4}$ by cancelling the common factors.

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Step 3.1.1

Cancel the common factor.

$\frac{y - 4}{(y - 6) (y - 3)} \cdot \frac{(y - 3) (y + 4)}{y + 4} \div \frac{y^{2} - 16}{y^{2} + 10 y + 24}$

Step 3.1.2

Rewrite the expression.

$\frac{y - 4}{(y - 6) (y - 3)} \cdot \frac{y - 3}{1} \div \frac{y^{2} - 16}{y^{2} + 10 y + 24}$

Step 3.2

Divide $y - 3$ by $1$ .

$\frac{y - 4}{(y - 6) (y - 3)} \cdot (y - 3) \div \frac{y^{2} - 16}{y^{2} + 10 y + 24}$

Step 4

Rewrite $16$ as $4^{2}$ .

$\frac{y - 4}{(y - 6) (y - 3)} \cdot (y - 3) \div \frac{y^{2} - 4^{2}}{y^{2} + 10 y + 24}$

Step 5

Since both terms are perfect squares, factor using the difference of squares formula, $a^{2} - b^{2} = (a + b) (a - b)$ where $a = y$ and $b = 4$ .

$\frac{y - 4}{(y - 6) (y - 3)} \cdot (y - 3) \div \frac{(y + 4) (y - 4)}{y^{2} + 10 y + 24}$

Step 6

Factor $y^{2} + 10 y + 24$ using the AC method.

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Step 6.1

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 $24$ and whose sum is $10$ .

$4, 6$

Step 6.2

Write the factored form using these integers.

$\frac{y - 4}{(y - 6) (y - 3)} \cdot (y - 3) \div \frac{(y + 4) (y - 4)}{(y + 4) (y + 6)}$

Step 7

Reduce the expression $\frac{(y + 4) (y - 4)}{(y + 4) (y + 6)}$ by cancelling the common factors.

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Step 7.1

Cancel the common factor.

$\frac{y - 4}{(y - 6) (y - 3)} \cdot (y - 3) \div \frac{(y + 4) (y - 4)}{(y + 4) (y + 6)}$

Step 7.2

Rewrite the expression.

$\frac{y - 4}{(y - 6) (y - 3)} \cdot (y - 3) \div \frac{y - 4}{y + 6}$