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Functions · Real functions

The absolute value function

A quality-control machine can't tell whether a rod is too long or too short: all it cares about is how far it deviates, in absolute value, from the target length. The absolute value function turns any "signed difference" into an always-positive distance, and that changes the shape of its graph in a very specific way.

Before you start, make sure you know: Piecewise-defined functions (4th ESO)
Before you start, make sure you know: Inequalities (4th ESO)

From absolute value to a piecewise function

Symmetric V-shaped graph opening upwards, with the vertex marked at its lowest point. vertex
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Express the function $f(x) = |3x - 6|$ as a piecewise function, clearly stating the intervals corresponding to each algebraic expression.

Express the function $f(x) = |3x - 6|$ as a piecewise function, clearly stating the intervals corresponding to each algebraic expression.

Solve
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Given the following piecewise function: $f(x) = \begin{cases} x + 4 & \text{if } x \ge -4 \\ -x - 4 & \text{if } x < -4 \end{cases}$ Write its analytical expression…

Given the following piecewise function:

$f(x) = \begin{cases} x + 4 & \text{if } x \ge -4 \\ -x - 4 & \text{if } x < -4 \end{cases}$

Write its analytical expression compactly using the modulus function.

Solve

The vertex: domain, range and intercepts

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Determine the domain and range of the function $h(x) = |x| + 5$. Justify your answer based on the properties of the modulus.

Determine the domain and range of the function $h(x) = |x| + 5$. Justify your answer based on the properties of the modulus.

Solve
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Determine the exact coordinates of the axis intercepts of the function $h(x) = |x - 3| - 5$.

Determine the exact coordinates of the axis intercepts of the function $h(x) = |x - 3| - 5$.

Solve

Quadratic and rational functions with absolute value

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Express the function $f(x) = |x^2 - 5x + 6|$ as a piecewise function. State in which interval or intervals the original parabola $y = x^2 - 5x + 6$ has been reflected…

Express the function $f(x) = |x^2 - 5x + 6|$ as a piecewise function. State in which interval or intervals the original parabola $y = x^2 - 5x + 6$ has been reflected across the x-axis.

Solve
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Express the rational function with a modulus $f(x) = \left| \frac{2x - 4}{x + 1} \right|$ as a piecewise function. Next, determine its domain and the equations of its…

Express the rational function with a modulus $f(x) = \left| \frac{2x - 4}{x + 1} \right|$ as a piecewise function. Next, determine its domain and the equations of its horizontal and vertical asymptotes.

Solve

Equations and inequalities with absolute value

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Find analytically the points of intersection between the modulus function $f(x) = |3x - 2|$ and the constant function $g(x) = 7$.

Find analytically the points of intersection between the modulus function $f(x) = |3x - 2|$ and the constant function $g(x) = 7$.

Solve
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A machine cuts metal rods with a target length of $250\text{ mm}$. The cutting error function is defined as $E(x) = |x - 250|$. If quality control requires that…

A machine cuts metal rods with a target length of $250\text{ mm}$. The cutting error function is defined as $E(x) = |x - 250|$. If quality control requires that $E(x) \le 1,5$, set up the corresponding inequality and determine the interval of valid rod lengths.

Solve

Summary

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