1.1.1 Identify variables:
Situation 1 (Linear):
- Independent variable: number of kilometres driven, $x$.
- Dependent variable: total rental cost in Rands, $f(x)$.
Situation 2 (Non-linear):
- Independent variable: radius of the circle, $r$.
- Dependent variable: area of the circle, $A$.
1.1.2 Write function rules:
Situation 1:
- Rental cost function: $$f(x) = 230 + 4.30x$$ where $x$ is kilometres driven.
Situation 2:
- Area of circle function: $$A(r) = \pi r^2$$
1.1.3 Create tables:
Situation 1:
| $x$ (km) | $f(x)$ (cost) |
| --- | --- |
| 0 | $230 + 4.30 \times 0 = 230$ |
| 10 | $230 + 4.30 \times 10 = 230 + 43 = 273$ |
| 25 | $230 + 4.30 \times 25 = 230 + 107.5 = 337.5$ |
| 50 | $230 + 4.30 \times 50 = 230 + 215 = 445$ |
Situation 2:
| $r$ (radius) | $A(r)$ (area) |
| --- | --- |
| 1 | $\pi \times 1^2 = \pi \approx 3.14$ |
| 2 | $\pi \times 2^2 = 4\pi \approx 12.57$ |
| 3 | $\pi \times 3^2 = 9\pi \approx 28.27$ |
| 4 | $\pi \times 4^2 = 16\pi \approx 50.27$ |
1.1.4 Sketch graphs:
- For Situation 1, plot $f(x) = 230 + 4.30x$ on axes with $x$ as kilometres (independent) and $f(x)$ as cost (dependent).
- For Situation 2, plot $A(r) = \pi r^2$ with $r$ as radius (independent) and $A(r)$ as area (dependent).
Both graphs show how dependent variables increase with the independent variable, linear for Situation 1 and quadratic for Situation 2.
Linear Nonlinear
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