Precalculus Examples

$\frac{z^{2} + 9 z + 20}{z^{2} + 12 z + 35} = \frac{z^{2} + 4 z}{z^{2} + 11 z + 28}$

Step 1

Factor each term.

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Step 1.1

Factor $z^{2} + 9 z + 20$ using the AC method.

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Step 1.1.1

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 $20$ and whose sum is $9$ .

$4, 5$

Step 1.1.2

Write the factored form using these integers.

$\frac{(z + 4) (z + 5)}{z^{2} + 12 z + 35} = \frac{z^{2} + 4 z}{z^{2} + 11 z + 28}$

Step 1.2

Factor $z^{2} + 12 z + 35$ using the AC method.

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Step 1.2.1

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 $35$ and whose sum is $12$ .

$5, 7$

Step 1.2.2

Write the factored form using these integers.

$\frac{(z + 4) (z + 5)}{(z + 5) (z + 7)} = \frac{z^{2} + 4 z}{z^{2} + 11 z + 28}$

Step 1.3

Reduce the expression $\frac{(z + 4) (z + 5)}{(z + 5) (z + 7)}$ by cancelling the common factors.

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Step 1.3.1

Cancel the common factor.

$\frac{(z + 4) (z + 5)}{(z + 5) (z + 7)} = \frac{z^{2} + 4 z}{z^{2} + 11 z + 28}$

Step 1.3.2

Rewrite the expression.

$\frac{z + 4}{z + 7} = \frac{z^{2} + 4 z}{z^{2} + 11 z + 28}$

Step 1.4

Factor $z$ out of $z^{2} + 4 z$ .

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Step 1.4.1

Factor $z$ out of $z^{2}$ .

$\frac{z + 4}{z + 7} = \frac{z \cdot z + 4 z}{z^{2} + 11 z + 28}$

Step 1.4.2

Factor $z$ out of $4 z$ .

$\frac{z + 4}{z + 7} = \frac{z \cdot z + z \cdot 4}{z^{2} + 11 z + 28}$

Step 1.4.3

Factor $z$ out of $z \cdot z + z \cdot 4$ .

$\frac{z + 4}{z + 7} = \frac{z (z + 4)}{z^{2} + 11 z + 28}$

Step 1.5

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

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Step 1.5.1

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 $28$ and whose sum is $11$ .

$4, 7$

Step 1.5.2

Write the factored form using these integers.

$\frac{z + 4}{z + 7} = \frac{z (z + 4)}{(z + 4) (z + 7)}$

Step 1.6

Reduce the expression $\frac{z (z + 4)}{(z + 4) (z + 7)}$ by cancelling the common factors.

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Step 1.6.1

Cancel the common factor.

$\frac{z + 4}{z + 7} = \frac{z (z + 4)}{(z + 4) (z + 7)}$

Step 1.6.2

Rewrite the expression.

$\frac{z + 4}{z + 7} = \frac{z}{z + 7}$

Step 2

Find the LCD of the terms in the equation.

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Step 2.1

Finding the LCD of a list of values is the same as finding the LCM of the denominators of those values.

$z + 7, z + 7$

Step 2.2

The LCM is the smallest positive number that all of the numbers divide into evenly.

1. List the prime factors of each number.

2. Multiply each factor the greatest number of times it occurs in either number.

Step 2.3

The number $1$ is not a prime number because it only has one positive factor, which is itself.

Not prime

Step 2.4

The LCM of $1, 1$ is the result of multiplying all prime factors the greatest number of times they occur in either number.

$1$

Step 2.5

The factor for $z + 7$ is $z + 7$ itself.

$(z + 7) = z + 7$

$(z + 7)$ occurs $1$ time.

Step 2.6

The LCM of $z + 7, z + 7$ is the result of multiplying all factors the greatest number of times they occur in either term.

$z + 7$

Step 3

Multiply each term in $\frac{z + 4}{z + 7} = \frac{z}{z + 7}$ by $z + 7$ to eliminate the fractions.

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Step 3.1

Multiply each term in $\frac{z + 4}{z + 7} = \frac{z}{z + 7}$ by $z + 7$ .

$\frac{z + 4}{z + 7} (z + 7) = \frac{z}{z + 7} (z + 7)$

Step 3.2

Simplify the left side.

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Step 3.2.1

Cancel the common factor of $z + 7$ .

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Step 3.2.1.1

Cancel the common factor.

$\frac{z + 4}{z + 7} (z + 7) = \frac{z}{z + 7} (z + 7)$

Step 3.2.1.2

Rewrite the expression.

$z + 4 = \frac{z}{z + 7} (z + 7)$

Step 3.3

Simplify the right side.

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Step 3.3.1

Cancel the common factor of $z + 7$ .

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Step 3.3.1.1

Cancel the common factor.

$z + 4 = \frac{z}{z + 7} (z + 7)$

Step 3.3.1.2

Rewrite the expression.

$z + 4 = z$

Step 4

Solve the equation.

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Step 4.1

Move all terms containing $z$ to the left side of the equation.

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Step 4.1.1

Subtract $z$ from both sides of the equation.

$z + 4 - z = 0$

Step 4.1.2

Combine the opposite terms in $z + 4 - z$ .

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Step 4.1.2.1

Subtract $z$ from $z$ .

$0 + 4 = 0$

Step 4.1.2.2

Add $0$ and $4$ .

$4 = 0$

Step 4.2

Since $4 \neq 0$ , there are no solutions.

No solution