Precalculus Examples

$\frac{6}{2 r (r + 6) (r - 6)} - \frac{r - 3}{3}$

Step 1

Cancel the common factor of $6$ and $2$ .

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Step 1.1

Factor $2$ out of $6$ .

$\frac{2 \cdot 3}{2 r (r + 6) (r - 6)} - \frac{r - 3}{3}$

Step 1.2

Cancel the common factors.

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Step 1.2.1

Factor $2$ out of $2 r (r + 6) (r - 6)$ .

$\frac{2 \cdot 3}{2 ((r (r + 6)) (r - 6))} - \frac{r - 3}{3}$

Step 1.2.2

Cancel the common factor.

$\frac{2 \cdot 3}{2 ((r (r + 6)) (r - 6))} - \frac{r - 3}{3}$

Step 1.2.3

Rewrite the expression.

$\frac{3}{(r (r + 6)) (r - 6)} - \frac{r - 3}{3}$

$\frac{3}{r (r + 6) (r - 6)} - \frac{r - 3}{3}$

Step 2

To write $\frac{3}{r (r + 6) (r - 6)}$ as a fraction with a common denominator, multiply by $\frac{3}{3}$ .

$\frac{3}{r (r + 6) (r - 6)} \cdot \frac{3}{3} - \frac{r - 3}{3}$

Step 3

To write $- \frac{r - 3}{3}$ as a fraction with a common denominator, multiply by $\frac{r (r + 6) (r - 6)}{r (r + 6) (r - 6)}$ .

$\frac{3}{r (r + 6) (r - 6)} \cdot \frac{3}{3} - \frac{r - 3}{3} \cdot \frac{r (r + 6) (r - 6)}{r (r + 6) (r - 6)}$

Step 4

Write each expression with a common denominator of $r (r + 6) (r - 6) \cdot 3$ , by multiplying each by an appropriate factor of $1$ .

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Step 4.1

Multiply $\frac{3}{r (r + 6) (r - 6)}$ by $\frac{3}{3}$ .

$\frac{3 \cdot 3}{r (r + 6) (r - 6) \cdot 3} - \frac{r - 3}{3} \cdot \frac{r (r + 6) (r - 6)}{r (r + 6) (r - 6)}$

Step 4.2

Multiply $\frac{r - 3}{3}$ by $\frac{r (r + 6) (r - 6)}{r (r + 6) (r - 6)}$ .

$\frac{3 \cdot 3}{r (r + 6) (r - 6) \cdot 3} - \frac{(r - 3) (r (r + 6) (r - 6))}{3 (r (r + 6) (r - 6))}$

Step 4.3

Reorder the factors of $r (r + 6) (r - 6) \cdot 3$ .

$\frac{3 \cdot 3}{3 r (r + 6) (r - 6)} - \frac{(r - 3) (r (r + 6) (r - 6))}{3 (r (r + 6) (r - 6))}$

Step 4.4

Reorder the factors of $3 (r (r + 6) (r - 6))$ .

$\frac{3 \cdot 3}{3 r (r + 6) (r - 6)} - \frac{(r - 3) (r (r + 6) (r - 6))}{3 r (r + 6) (r - 6)}$

Step 5

Combine the numerators over the common denominator.

$\frac{3 \cdot 3 - (r - 3) (r (r + 6) (r - 6))}{3 r (r + 6) (r - 6)}$

Step 6

Simplify the numerator.

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Step 6.1

Multiply $3$ by $3$ .

$\frac{9 - (r - 3) (r (r + 6) (r - 6))}{3 r (r + 6) (r - 6)}$

Step 6.2

Apply the distributive property.

$\frac{9 + (- r - - 3) (r (r + 6) (r - 6))}{3 r (r + 6) (r - 6)}$

Step 6.3

Multiply $- 1$ by $- 3$ .

$\frac{9 + (- r + 3) (r (r + 6) (r - 6))}{3 r (r + 6) (r - 6)}$

Step 6.4

Apply the distributive property.

$\frac{9 + (- r + 3) ((r \cdot r + r \cdot 6) (r - 6))}{3 r (r + 6) (r - 6)}$

Step 6.5

Multiply $r$ by $r$ .

$\frac{9 + (- r + 3) ((r^{2} + r \cdot 6) (r - 6))}{3 r (r + 6) (r - 6)}$

Step 6.6

Move $6$ to the left of $r$ .

$\frac{9 + (- r + 3) ((r^{2} + 6 \cdot r) (r - 6))}{3 r (r + 6) (r - 6)}$

Step 6.7

Expand $(r^{2} + 6 r) (r - 6)$ using the FOIL Method.

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Step 6.7.1

Apply the distributive property.

$\frac{9 + (- r + 3) (r^{2} (r - 6) + 6 r (r - 6))}{3 r (r + 6) (r - 6)}$

Step 6.7.2

Apply the distributive property.

$\frac{9 + (- r + 3) (r^{2} r + r^{2} \cdot - 6 + 6 r (r - 6))}{3 r (r + 6) (r - 6)}$

Step 6.7.3

Apply the distributive property.

$\frac{9 + (- r + 3) (r^{2} r + r^{2} \cdot - 6 + 6 r \cdot r + 6 r \cdot - 6)}{3 r (r + 6) (r - 6)}$

Step 6.8

Simplify and combine like terms.

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Step 6.8.1

Simplify each term.

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Step 6.8.1.1

Multiply $r^{2}$ by $r$ by adding the exponents.

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Step 6.8.1.1.1

Multiply $r^{2}$ by $r$ .

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Step 6.8.1.1.1.1

Raise $r$ to the power of $1$ .

$\frac{9 + (- r + 3) (r^{2} r^{1} + r^{2} \cdot - 6 + 6 r \cdot r + 6 r \cdot - 6)}{3 r (r + 6) (r - 6)}$

Step 6.8.1.1.1.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{9 + (- r + 3) (r^{2 + 1} + r^{2} \cdot - 6 + 6 r \cdot r + 6 r \cdot - 6)}{3 r (r + 6) (r - 6)}$

Step 6.8.1.1.2

Add $2$ and $1$ .

$\frac{9 + (- r + 3) (r^{3} + r^{2} \cdot - 6 + 6 r \cdot r + 6 r \cdot - 6)}{3 r (r + 6) (r - 6)}$

Step 6.8.1.2

Move $- 6$ to the left of $r^{2}$ .

$\frac{9 + (- r + 3) (r^{3} - 6 \cdot r^{2} + 6 r \cdot r + 6 r \cdot - 6)}{3 r (r + 6) (r - 6)}$

Step 6.8.1.3

Multiply $r$ by $r$ by adding the exponents.

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Step 6.8.1.3.1

Move $r$ .

$\frac{9 + (- r + 3) (r^{3} - 6 r^{2} + 6 (r \cdot r) + 6 r \cdot - 6)}{3 r (r + 6) (r - 6)}$

Step 6.8.1.3.2

Multiply $r$ by $r$ .

$\frac{9 + (- r + 3) (r^{3} - 6 r^{2} + 6 r^{2} + 6 r \cdot - 6)}{3 r (r + 6) (r - 6)}$

Step 6.8.1.4

Multiply $- 6$ by $6$ .

$\frac{9 + (- r + 3) (r^{3} - 6 r^{2} + 6 r^{2} - 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.8.2

Add $- 6 r^{2}$ and $6 r^{2}$ .

$\frac{9 + (- r + 3) (r^{3} + 0 - 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.8.3

Add $r^{3}$ and $0$ .

$\frac{9 + (- r + 3) (r^{3} - 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.9

Expand $(- r + 3) (r^{3} - 36 r)$ using the FOIL Method.

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Step 6.9.1

Apply the distributive property.

$\frac{9 - r (r^{3} - 36 r) + 3 (r^{3} - 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.9.2

Apply the distributive property.

$\frac{9 - r \cdot r^{3} - r (- 36 r) + 3 (r^{3} - 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.9.3

Apply the distributive property.

$\frac{9 - r \cdot r^{3} - r (- 36 r) + 3 r^{3} + 3 (- 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.10

Simplify each term.

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Step 6.10.1

Multiply $r$ by $r^{3}$ by adding the exponents.

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Step 6.10.1.1

Move $r^{3}$ .

$\frac{9 - (r^{3} r) - r (- 36 r) + 3 r^{3} + 3 (- 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.10.1.2

Multiply $r^{3}$ by $r$ .

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Step 6.10.1.2.1

Raise $r$ to the power of $1$ .

$\frac{9 - (r^{3} r^{1}) - r (- 36 r) + 3 r^{3} + 3 (- 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.10.1.2.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{9 - r^{3 + 1} - r (- 36 r) + 3 r^{3} + 3 (- 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.10.1.3

Add $3$ and $1$ .

$\frac{9 - r^{4} - r (- 36 r) + 3 r^{3} + 3 (- 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.10.2

Rewrite using the commutative property of multiplication.

$\frac{9 - r^{4} - 1 \cdot - 36 r \cdot r + 3 r^{3} + 3 (- 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.10.3

Multiply $r$ by $r$ by adding the exponents.

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Step 6.10.3.1

Move $r$ .

$\frac{9 - r^{4} - 1 \cdot - 36 (r \cdot r) + 3 r^{3} + 3 (- 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.10.3.2

Multiply $r$ by $r$ .

$\frac{9 - r^{4} - 1 \cdot - 36 r^{2} + 3 r^{3} + 3 (- 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.10.4

Multiply $- 1$ by $- 36$ .

$\frac{9 - r^{4} + 36 r^{2} + 3 r^{3} + 3 (- 36 r)}{3 r (r + 6) (r - 6)}$

Step 6.10.5

Multiply $- 36$ by $3$ .

$\frac{9 - r^{4} + 36 r^{2} + 3 r^{3} - 108 r}{3 r (r + 6) (r - 6)}$

Step 6.11

Reorder terms.

$\frac{- r^{4} + 3 r^{3} + 36 r^{2} - 108 r + 9}{3 r (r + 6) (r - 6)}$

Step 7

Simplify with factoring out.

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Step 7.1

Factor $- 1$ out of $- r^{4}$ .

$\frac{- (r^{4}) + 3 r^{3} + 36 r^{2} - 108 r + 9}{3 r (r + 6) (r - 6)}$

Step 7.2

Factor $- 1$ out of $3 r^{3}$ .

$\frac{- (r^{4}) - (- 3 r^{3}) + 36 r^{2} - 108 r + 9}{3 r (r + 6) (r - 6)}$

Step 7.3

Factor $- 1$ out of $- (r^{4}) - (- 3 r^{3})$ .

$\frac{- (r^{4} - 3 r^{3}) + 36 r^{2} - 108 r + 9}{3 r (r + 6) (r - 6)}$

Step 7.4

Factor $- 1$ out of $36 r^{2}$ .

$\frac{- (r^{4} - 3 r^{3}) - (- 36 r^{2}) - 108 r + 9}{3 r (r + 6) (r - 6)}$

Step 7.5

Factor $- 1$ out of $- (r^{4} - 3 r^{3}) - (- 36 r^{2})$ .

$\frac{- (r^{4} - 3 r^{3} - 36 r^{2}) - 108 r + 9}{3 r (r + 6) (r - 6)}$

Step 7.6

Factor $- 1$ out of $- 108 r$ .

$\frac{- (r^{4} - 3 r^{3} - 36 r^{2}) - (108 r) + 9}{3 r (r + 6) (r - 6)}$

Step 7.7

Factor $- 1$ out of $- (r^{4} - 3 r^{3} - 36 r^{2}) - (108 r)$ .

$\frac{- (r^{4} - 3 r^{3} - 36 r^{2} + 108 r) + 9}{3 r (r + 6) (r - 6)}$

Step 7.8

Rewrite $9$ as $- 1 (- 9)$ .

$\frac{- (r^{4} - 3 r^{3} - 36 r^{2} + 108 r) - 1 (- 9)}{3 r (r + 6) (r - 6)}$

Step 7.9

Factor $- 1$ out of $- (r^{4} - 3 r^{3} - 36 r^{2} + 108 r) - 1 (- 9)$ .

$\frac{- (r^{4} - 3 r^{3} - 36 r^{2} + 108 r - 9)}{3 r (r + 6) (r - 6)}$

Step 7.10

Simplify the expression.

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Step 7.10.1

Rewrite $- (r^{4} - 3 r^{3} - 36 r^{2} + 108 r - 9)$ as $- 1 (r^{4} - 3 r^{3} - 36 r^{2} + 108 r - 9)$ .

$\frac{- 1 (r^{4} - 3 r^{3} - 36 r^{2} + 108 r - 9)}{3 r (r + 6) (r - 6)}$

Step 7.10.2

Move the negative in front of the fraction.

$- \frac{r^{4} - 3 r^{3} - 36 r^{2} + 108 r - 9}{3 r (r + 6) (r - 6)}$