Function Inverse Composition
1) Given the function $f(x) = 2x - 5$:
1. a) Find $f'(x)$, the derivative of $f(x)$.
Since $f(x) = 2x - 5$, the derivative is the rate of change of $f$ with respect to $x$.
$$f'(x) = \frac{d}{dx}(2x - 5) = 2$$
1. b) Find $f^{-1}(2)$, the inverse function's value at 2.
To find $f^{-1}(2)$, solve $f(x) = 2$ for $x$:
$$2x - 5 = 2$$
$$2x = 7$$
$$x = \frac{7}{2} = 3.5$$
1. c) Find $x$ if $f(f(f(x)))=x$.
Calculate the triple composition:
$$f(x) = 2x - 5$$
$$f(f(x)) = f(2x - 5) = 2(2x - 5) - 5 = 4x - 10 - 5 = 4x - 15$$
$$f(f(f(x))) = f(4x - 15) = 2(4x - 15) - 5 = 8x - 30 - 5 = 8x - 35$$
Set equal to $x$:
$$8x - 35 = x$$
$$8x - x = 35$$
$$7x = 35$$
$$x = 5$$
2) Evaluate $\left(\frac{8}{27}\right)^{1/3}$.
Recall: $a^{1/3}$ is the cube root of $a$.
$$\left(\frac{8}{27}\right)^{1/3} = \frac{8^{1/3}}{27^{1/3}} = \frac{2}{3}$$
3) Factorize completely $3x^2 - 27x$.
Factor out greatest common factor $3x$:
$$3x^2 - 27x = 3x(x - 9)$$
4) Given the speed-time graph with speed dropping linearly from 9 to 0 in 9 seconds:
4.a) Find the acceleration during the first 8 seconds.
Acceleration = change in speed / time:
$$a = \frac{v_{final} - v_{initial}}{t} = \frac{0 - 9}{9} = -1 \text{ m/s}^2$$
During first 8 seconds, speed decreases linearly so acceleration is constant:
$$a = -1 \text{ m/s}^2$$
4.b) Find distance covered in first 14 seconds.
Speed decreases from 9 to 0 in 9 seconds, then stays at 0 from 9 to 14 seconds (assumed from graph).
Distance is area under speed-time graph.
Area from 0 to 9 seconds is triangle:
$$\text{Area} = \frac{1}{2} \times 9 \times 9 = 40.5 \text{ units}$$
From 9 to 14 seconds speed is 0, so distance = 0.
Total distance:
$$40.5$$
4.c) Find average speed if total distance in 14 seconds is 40.5:
$$\text{Average speed} = \frac{\text{Distance}}{\text{Time}} = \frac{40.5}{14} \approx 2.89 \text{ m/s}$$
4.d) Solve the equation $2x + 3 = \frac{1}{6}$.
$$2x = \frac{1}{6} - 3 = \frac{1}{6} - \frac{18}{6} = -\frac{17}{6}$$
$$x = -\frac{17}{12}$$
4.e) Find $\int (6x^2 - 2x + 7) dx$.
Integrate term-by-term:
$$\int 6x^2 dx = 6 \cdot \frac{x^3}{3} = 2x^3$$
$$\int -2x dx = -2 \cdot \frac{x^2}{2} = -x^2$$
$$\int 7 dx = 7x$$
Therefore:
$$\int (6x^2 - 2x + 7) dx = 2x^3 - x^2 + 7x + C$$
5) Given $f(x) = x - 4$, $h(x) = 2x + 3$:
5.a) Find $h^{-1}(x)$.
Let $y = h(x) = 2x + 3$. Solve for $x$:
$$y = 2x + 3$$
$$2x = y - 3$$
$$x = \frac{y - 3}{2}$$
So,
$$h^{-1}(x) = \frac{x - 3}{2}$$
5.b) Find $h^{-1}(5)$:
$$h^{-1}(5) = \frac{5 - 3}{2} = \frac{2}{2} = 1$$
5.c) Find $hf(x)$, composition $h(f(x))$:
$$hf(x) = h(f(x)) = h(x - 4) = 2(x - 4) + 3 = 2x - 8 + 3 = 2x - 5$$