Algebra Examples

$f (x) = \frac{7 x + 4}{x + 3}$ $g (x) = \frac{3 x - 4}{7 - x}$

Step 1

Set up the composite result function.

$g (f (x))$

Step 2

Evaluate $g (\frac{7 x + 4}{x + 3})$ by substituting in the value of $f$ into $g$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{3 (\frac{7 x + 4}{x + 3}) - 4}{7 - (\frac{7 x + 4}{x + 3})}$

Step 3

Multiply the numerator and denominator of the fraction by $x + 3$ .

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Step 3.1

Multiply $\frac{3 \frac{7 x + 4}{x + 3} - 4}{7 - \frac{7 x + 4}{x + 3}}$ by $\frac{x + 3}{x + 3}$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{x + 3}{x + 3} \cdot \frac{3 (\frac{7 x + 4}{x + 3}) - 4}{7 - \frac{7 x + 4}{x + 3}}$

Step 3.2

Combine.

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (3 (\frac{7 x + 4}{x + 3}) - 4)}{(x + 3) (7 - \frac{7 x + 4}{x + 3})}$

Step 4

Apply the distributive property.

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (3 (\frac{7 x + 4}{x + 3})) + (x + 3) \cdot - 4}{(x + 3) \cdot 7 + (x + 3) (- \frac{7 x + 4}{x + 3})}$

Step 5

Cancel the common factor of $x + 3$ .

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Step 5.1

Move the leading negative in $- \frac{7 x + 4}{x + 3}$ into the numerator.

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (3 (\frac{7 x + 4}{x + 3})) + (x + 3) \cdot - 4}{(x + 3) \cdot 7 + (x + 3) (\frac{- (7 x + 4)}{x + 3})}$

Step 5.2

Cancel the common factor.

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (3 (\frac{7 x + 4}{x + 3})) + (x + 3) \cdot - 4}{(x + 3) \cdot 7 + (x + 3) (\frac{- (7 x + 4)}{x + 3})}$

Step 5.3

Rewrite the expression.

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (3 (\frac{7 x + 4}{x + 3})) + (x + 3) \cdot - 4}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6

Simplify the numerator.

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Step 6.1

Factor $x + 3$ out of $(x + 3) \cdot 3 \frac{7 x + 4}{x + 3} + (x + 3) \cdot - 4$ .

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Step 6.1.1

Factor $x + 3$ out of $(x + 3) \cdot 3 \frac{7 x + 4}{x + 3}$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (3 (\frac{7 x + 4}{x + 3})) + (x + 3) \cdot - 4}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.1.2

Factor $x + 3$ out of $(x + 3) \cdot - 4$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (3 (\frac{7 x + 4}{x + 3})) + (x + 3) (- 4)}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.1.3

Factor $x + 3$ out of $(x + 3) (3 \frac{7 x + 4}{x + 3}) + (x + 3) (- 4)$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (3 (\frac{7 x + 4}{x + 3}) - 4)}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.2

Combine $3$ and $\frac{7 x + 4}{x + 3}$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{3 (7 x + 4)}{x + 3} - 4)}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.3

To write $- 4$ as a fraction with a common denominator, multiply by $\frac{x + 3}{x + 3}$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{3 (7 x + 4)}{x + 3} - 4 \cdot \frac{x + 3}{x + 3})}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.4

Combine $- 4$ and $\frac{x + 3}{x + 3}$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{3 (7 x + 4)}{x + 3} + \frac{- 4 (x + 3)}{x + 3})}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.5

Combine the numerators over the common denominator.

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{3 (7 x + 4) - 4 (x + 3)}{x + 3})}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.6

Rewrite $\frac{3 (7 x + 4) - 4 (x + 3)}{x + 3}$ in a factored form.

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Step 6.6.1

Apply the distributive property.

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{3 (7 x) + 3 \cdot 4 - 4 (x + 3)}{x + 3})}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.6.2

Multiply $7$ by $3$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{21 x + 3 \cdot 4 - 4 (x + 3)}{x + 3})}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.6.3

Multiply $3$ by $4$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{21 x + 12 - 4 (x + 3)}{x + 3})}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.6.4

Apply the distributive property.

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{21 x + 12 - 4 x - 4 \cdot 3}{x + 3})}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.6.5

Multiply $- 4$ by $3$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{21 x + 12 - 4 x - 12}{x + 3})}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.6.6

Subtract $4 x$ from $21 x$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{17 x + 12 - 12}{x + 3})}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.6.7

Subtract $12$ from $12$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{17 x + 0}{x + 3})}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 6.6.8

Add $17 x$ and $0$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{17 x}{x + 3})}{(x + 3) \cdot 7 - (7 x + 4)}$

Step 7

Simplify the denominator.

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Step 7.1

Apply the distributive property.

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{17 x}{x + 3})}{x \cdot 7 + 3 \cdot 7 - (7 x + 4)}$

Step 7.2

Move $7$ to the left of $x$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{17 x}{x + 3})}{7 \cdot x + 3 \cdot 7 - (7 x + 4)}$

Step 7.3

Multiply $3$ by $7$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{17 x}{x + 3})}{7 \cdot x + 21 - (7 x + 4)}$

Step 7.4

Apply the distributive property.

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{17 x}{x + 3})}{7 x + 21 - (7 x) - 1 \cdot 4}$

Step 7.5

Multiply $7$ by $- 1$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{17 x}{x + 3})}{7 x + 21 - 7 x - 1 \cdot 4}$

Step 7.6

Multiply $- 1$ by $4$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{17 x}{x + 3})}{7 x + 21 - 7 x - 4}$

Step 7.7

Subtract $7 x$ from $7 x$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{17 x}{x + 3})}{0 + 21 - 4}$

Step 7.8

Add $0$ and $21$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{17 x}{x + 3})}{21 - 4}$

Step 7.9

Subtract $4$ from $21$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{(x + 3) (\frac{17 x}{x + 3})}{17}$

Step 8

Reduce the expression by cancelling the common factors.

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Step 8.1

Factor $\frac{17 x}{x + 3}$ out of $\frac{(x + 3) \frac{17 x}{x + 3}}{17}$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{17 x}{x + 3} \cdot \frac{x + 3}{17}$

Step 8.2

Cancel the common factor of $17$ .

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Step 8.2.1

Factor $17$ out of $17 x$ .

$g (\frac{7 x + 4}{x + 3}) = \frac{17 (x)}{x + 3} \cdot \frac{x + 3}{17}$

Step 8.2.2

Cancel the common factor.

$g (\frac{7 x + 4}{x + 3}) = \frac{17 x}{x + 3} \cdot \frac{x + 3}{17}$

Step 8.2.3

Rewrite the expression.

$g (\frac{7 x + 4}{x + 3}) = \frac{x}{x + 3} \cdot (x + 3)$

Step 8.3

Cancel the common factor of $x + 3$ .

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Step 8.3.1

Cancel the common factor.

$g (\frac{7 x + 4}{x + 3}) = \frac{x}{x + 3} \cdot (x + 3)$

Step 8.3.2

Rewrite the expression.

$g (\frac{7 x + 4}{x + 3}) = x$