Domain Range Functions
1. Find the domain and range of each relation using interval notation, and determine if it is a function.
- Top-left graph (rational function with vertical asymptote at $x=1$ and horizontal asymptote at $y=0$):
- Domain excludes $x=1$ where the vertical asymptote is, so:
$$\text{Domain} = (-\infty, 1) \cup (1, \infty)$$
- Range excludes $y=0$ because of horizontal asymptote:
$$\text{Range} = (-\infty, 0) \cup (0, \infty)$$
- Function? Yes, since each $x$ corresponds to exactly one $y$ except $x=1$ which is excluded.
- Top-right graph (sinusoidal wave):
- Domain covers all real numbers:
$$\text{Domain} = (-\infty, \infty)$$
- Range oscillates between minimum and maximum values, typically between $-1$ and $1$, so:
$$\text{Range} = [-1, 1]$$
- Function? Yes, the sinusoidal graph passes vertical line test.
- Bottom-left graph (piecewise linear, downward then upward slope):
- Domain covers all real numbers (graph extends left and right indefinitely):
$$\text{Domain} = (-\infty, \infty)$$
- Range depends on the values the graph attains, assuming minimum near zero and extending upwards and downwards, plausible approximate range:
$$\text{Range} = (-\infty, \infty)$$
- Function? Yes, each input has only one output.
2. Find $f(-7)$ for $f(x)$ defined by the top-left graph.
Since the top-left graph is a rational function with vertical asymptote at $x=1$. The function likely behaves as $f(x) = \frac{1}{x-1}$ or similar. Evaluate $f(-7)$:
$$f(-7) = \frac{1}{-7-1} = \frac{1}{-8} = -\frac{1}{8}$$
3. Evaluate $f(2x + 3)$ where $f(x) = -x^2 + 3x + 10$.
1. Substitute $2x + 3$ in place of $x$:
$$f(2x + 3) = - (2x + 3)^2 + 3(2x + 3) + 10$$
2. Expand the square:
$$(2x + 3)^2 = 4x^2 + 12x + 9$$
3. Substitute back:
$$= - (4x^2 + 12x + 9) + 6x + 9 + 10$$
4. Distribute the negative:
$$= -4x^2 -12x -9 + 6x + 9 + 10$$
5. Combine like terms:
$$= -4x^2 -6x + 10$$
4. Find zeros and y-intercept for $f(x) = 4x^4 - 17x^2 + 4$.
1. Set $f(x) = 0$:
$$4x^4 - 17x^2 + 4 = 0$$
2. Substitute $u = x^2$:
$$4u^2 - 17u + 4 = 0$$
3. Solve quadratic using quadratic formula:
$$u = \frac{17 \pm \sqrt{(-17)^2 - 4 \times 4 \times 4}}{2 \times 4} = \frac{17 \pm \sqrt{289 - 64}}{8} = \frac{17 \pm \sqrt{225}}{8} = \frac{17 \pm 15}{8}$$
4. Calculate roots:
$$u_1 = \frac{17 + 15}{8} = 4$$
$$u_2 = \frac{17 - 15}{8} = \frac{2}{8} = \frac{1}{4}$$
5. Substitute back $x^2 = u$:
$$x^2 = 4 \rightarrow x = \pm 2$$
$$x^2 = \frac{1}{4} \rightarrow x = \pm \frac{1}{2}$$
Zeros are $x = -2, -\frac{1}{2}, \frac{1}{2}, 2$.
6. Y-intercept is $f(0)$:
$$f(0) = 4\times0 - 17\times0 + 4 = 4$$
5. Find zeros and y-intercept for $f(x) = x^6 - 81x^4$.
1. Factor:
$$f(x) = x^4(x^2 - 81) = x^4(x - 9)(x + 9)$$
2. Set each factor to zero:
$$x^4 = 0 \Rightarrow x = 0$$
$$x - 9 = 0 \Rightarrow x = 9$$
$$x + 9 = 0 \Rightarrow x = -9$$
Zeros: $x = -9, 0, 9$
3. Y-intercept:
$$f(0) = 0^6 - 81\times 0^4 = 0$$