Rational Functions Domain Range 1674Ed
1. **Problem:** Find the domain and range of the rational function $g(x) = \frac{2}{x - 5}$.
2. **Domain:** The domain is all real numbers except where the denominator is zero.
Set denominator equal to zero:
$$x - 5 = 0 \implies x = 5$$
So, domain is:
$$\{x \mid x \neq 5\}$$
3. **Range:** For $g(x) = \frac{2}{x - 5}$, the function can take any real value except zero because the numerator is constant and denominator can be any real number except zero.
Set $y = \frac{2}{x - 5}$ and solve for $x$:
$$y = \frac{2}{x - 5} \implies x - 5 = \frac{2}{y} \implies x = 5 + \frac{2}{y}$$
For $x$ to be real, $y \neq 0$.
So, range is:
$$\{y \mid y \neq 0\}$$
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1. **Problem:** Find the domain and range of the rational function $h(x) = \frac{2x}{(x + 2)(x - 2)}$.
2. **Domain:** Denominator cannot be zero:
$$(x + 2)(x - 2) = 0 \implies x = -2 \text{ or } x = 2$$
Domain:
$$\{x \mid x \neq -2, x \neq 2\}$$
3. **Range:** Set $y = \frac{2x}{(x + 2)(x - 2)} = \frac{2x}{x^2 - 4}$.
Rewrite:
$$y = \frac{2x}{x^2 - 4} \implies y(x^2 - 4) = 2x \implies yx^2 - 4y = 2x$$
Rearranged:
$$yx^2 - 2x - 4y = 0$$
Consider as quadratic in $x$:
$$yx^2 - 2x - 4y = 0$$
Discriminant:
$$\Delta = (-2)^2 - 4(y)(-4y) = 4 + 16y^2 = 4(1 + 4y^2) > 0$$
Since $\Delta > 0$ for all real $y$, there are real $x$ solutions for all $y$.
Check if $y=0$ is possible:
$$0 = \frac{2x}{x^2 - 4} \implies 2x = 0 \implies x=0$$
$x=0$ is in domain, so $y=0$ is in range.
Therefore, range is all real numbers:
$$\{y \mid y \in \mathbb{R}\}$$
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1. **Problem:** Find the domain and range of the rational function $r(x) = \frac{x^2 - 4}{-x^2 - 2x + 3}$.
2. **Domain:** Denominator cannot be zero:
$$-x^2 - 2x + 3 = 0 \implies x^2 + 2x - 3 = 0$$
Solve quadratic:
$$x = \frac{-2 \pm \sqrt{4 + 12}}{2} = \frac{-2 \pm 4}{2}$$
Roots:
$$x = 1 \text{ or } x = -3$$
Domain:
$$\{x \mid x \neq 1, x \neq -3\}$$
3. **Range:** Set $y = \frac{x^2 - 4}{-x^2 - 2x + 3}$.
Rewrite denominator:
$$-x^2 - 2x + 3 = -(x^2 + 2x - 3)$$
So,
$$y = \frac{x^2 - 4}{-(x^2 + 2x - 3)} = -\frac{x^2 - 4}{x^2 + 2x - 3}$$
Cross-multiplied:
$$y(x^2 + 2x - 3) = -(x^2 - 4)$$
Expand:
$$yx^2 + 2yx - 3y = -x^2 + 4$$
Bring all terms to one side:
$$(y + 1)x^2 + 2yx - 3y - 4 = 0$$
Consider as quadratic in $x$:
$$A = y + 1, B = 2y, C = -3y - 4$$
Discriminant:
$$\Delta = B^2 - 4AC = (2y)^2 - 4(y + 1)(-3y - 4) = 4y^2 + 4(y + 1)(3y + 4)$$
Calculate:
$$4y^2 + 4[(y)(3y + 4) + 1(3y + 4)] = 4y^2 + 4(3y^2 + 4y + 3y + 4) = 4y^2 + 4(3y^2 + 7y + 4)$$
$$= 4y^2 + 12y^2 + 28y + 16 = 16y^2 + 28y + 16$$
For real $x$, $\Delta \geq 0$:
$$16y^2 + 28y + 16 \geq 0$$
Divide by 4:
$$4y^2 + 7y + 4 \geq 0$$
Find roots:
$$y = \frac{-7 \pm \sqrt{49 - 64}}{8} = \frac{-7 \pm \sqrt{-15}}{8}$$
Discriminant negative, so quadratic always positive.
Therefore, $\Delta > 0$ for all real $y$.
Check if denominator $A = y + 1 = 0$ (to avoid division by zero in quadratic formula):
If $y = -1$, then equation becomes:
$$0 \cdot x^2 + 2(-1)x - 3(-1) - 4 = -2x + 3 - 4 = -2x - 1 = 0$$
Solve:
$$-2x - 1 = 0 \implies x = -\frac{1}{2}$$
Check if $x = -\frac{1}{2}$ is in domain:
Denominator at $x = -\frac{1}{2}$:
$$-\left(-\frac{1}{2}\right)^2 - 2\left(-\frac{1}{2}\right) + 3 = -\frac{1}{4} + 1 + 3 = 3.75 \neq 0$$
So $y = -1$ is in range.
Hence, range is all real numbers:
$$\{y \mid y \in \mathbb{R}\}$$
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1. **Problem:** Find the domain and range of the rational function $m(x) = \frac{x^2 - x - 12}{x^2 - 3x - 4}$.
2. **Domain:** Denominator cannot be zero:
$$x^2 - 3x - 4 = 0$$
Factor:
$$(x - 4)(x + 1) = 0 \implies x = 4 \text{ or } x = -1$$
Domain:
$$\{x \mid x \neq 4, x \neq -1\}$$
3. **Range:** Set
$$y = \frac{x^2 - x - 12}{x^2 - 3x - 4}$$
Factor numerator and denominator:
$$x^2 - x - 12 = (x - 4)(x + 3)$$
$$x^2 - 3x - 4 = (x - 4)(x + 1)$$
Simplify:
$$y = \frac{(x - 4)(x + 3)}{(x - 4)(x + 1)}$$
For $x \neq 4$, cancel $(x - 4)$:
$$y = \frac{x + 3}{x + 1}$$
Rewrite:
$$y = \frac{x + 3}{x + 1} \implies y(x + 1) = x + 3 \implies yx + y = x + 3$$
Rearranged:
$$(y - 1)x = 3 - y$$
If $y \neq 1$:
$$x = \frac{3 - y}{y - 1}$$
Check if $x$ is in domain:
$x \neq 4$ and $x \neq -1$.
Set $x = 4$:
$$4 = \frac{3 - y}{y - 1} \implies 4(y - 1) = 3 - y \implies 4y - 4 = 3 - y \implies 5y = 7 \implies y = \frac{7}{5}$$
Set $x = -1$:
$$-1 = \frac{3 - y}{y - 1} \implies -1(y - 1) = 3 - y \implies -y + 1 = 3 - y \implies 1 = 3$$
Contradiction, so $y = \frac{7}{5}$ is the only value excluded from range.
If $y = 1$:
$$y = 1 = \frac{x + 3}{x + 1} \implies x + 3 = x + 1 \implies 3 = 1$$
Contradiction, so $y = 1$ is not in range.
Therefore, range excludes $y = 1$ and $y = \frac{7}{5}$:
$$\{y \mid y \neq 1, y \neq \frac{7}{5}\}$$
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**Final answers in set builder notation:**
- $g(x)$ domain: $\{x \mid x \neq 5\}$
- $g(x)$ range: $\{y \mid y \neq 0\}$
- $h(x)$ domain: $\{x \mid x \neq -2, x \neq 2\}$
- $h(x)$ range: $\{y \mid y \in \mathbb{R}\}$
- $r(x)$ domain: $\{x \mid x \neq 1, x \neq -3\}$
- $r(x)$ range: $\{y \mid y \in \mathbb{R}\}$
- $m(x)$ domain: $\{x \mid x \neq 4, x \neq -1\}$
- $m(x)$ range: $\{y \mid y \neq 1, y \neq \frac{7}{5}\}$