Mon Prof Augmenté
Straight-Line Growth
Age 14 · Maths
An affine function starts at a value where its line crosses the vertical axis. Then it adds the same amount for every equal step to the right.
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In the picture
- The point where the line meets the vertical axis: the starting value.
- A marked point one step right: the value after one equal step.
- A marked point two steps right: the value after two equal steps.
- The line segment between the marked points: equal vertical rise for equal horizontal run.
Examples
- A phone plan with a fixed monthly fee plus a set charge for each gigabyte.
- A taxi fare with a starting charge plus a fixed price per kilometer.
Key takeaways
- The graph is a straight line because the rate of change stays constant.
- The point on the vertical axis gives the initial value.
Quiz: Straight-Line Growth (Age 14)
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What does the point where an affine function’s line crosses the vertical axis represent?
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Why is the graph of an affine function a straight line?
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For every equal step to the right on an affine function’s line, what happens to the vertical rise?
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