Chapter 1: Problem 23
Make a conjecture about the relationship between the graph of \(y=f(x)\) and the graph of \(y=|f(x)|\); check your conjecture with some specific functions.
Short Answer
Expert verified
\(|f(x)|\) reflects negative parts of \(f(x)\) above the x-axis.
Step by step solution
01
Understanding the Function Transformations
When dealing with transformations like moving from \(y = f(x)\) to \(y = |f(x)|\), the effect is that all the negative values of \(f(x)\) get reflected above the x-axis. This means the parts of the graph that were below the x-axis reflect to become positive, while the points at or above the x-axis remain unchanged.
02
Analyze Specific Function – Linear Function
Consider the function \(f(x) = x - 2\). The graph of \(y = f(x)\) crosses the x-axis at \(x = 2\). The part of the line below the x-axis (for \(x < 2\)) flips above it in \(y = |f(x)|\). Therefore, for \(x < 2\), the graph of \(y = |f(x)|\) will have the equation \(y = -(x - 2) = 2 - x\).
03
Analyze Specific Function – Quadratic Function
Consider the function \(f(x) = x^2 - 4\), a parabola that opens upwards with roots at \(x = -2\) and \(x = 2\). Below the x-axis for \(-2 < x < 2\), the graph is reflected above the x-axis for \(y = |f(x)|\). The section of \(f(x)\) between the roots becomes positive, effectively making the graph of \(y = |f(x)|\) a 'W' shape with the bottom part of \(y = f(x)\) flipped.
04
Observe General Pattern
In general, when moving from \(y = f(x)\) to \(y = |f(x)|\), any part where \(f(x)\) is negative is reflected vertically above the x-axis, while parts where \(f(x)\) is positive remain unchanged. This occurs always, resulting in a graph that looks like the original for positive sections and mirrored for negatives.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Function Transformations
When you transform a function, you convert its graph or shape in a specific way, often to make it easier to understand or analyze. One common transformation is changing the graph of a function like \( y = f(x) \) to \( y = |f(x)| \).
This particular transformation affects only the portions of the graph that are negative.
Here's what happens:
This particular transformation affects only the portions of the graph that are negative.
Here's what happens:
- The negative segments of the function are reflected upwards.
- All the values at or above the x-axis stay exactly as they are.
Graph Reflections
Graph reflections can be a fascinating aspect of visualizing mathematical functions. When reflecting the graph of a function \( y = f(x) \) about the x-axis using absolute values, you create \( y = |f(x)| \).
This process affects the negative portions beneath the x-axis, flipping them upward.
Some points to consider:
This process affects the negative portions beneath the x-axis, flipping them upward.
Some points to consider:
- If \( f(x) \) is negative at a point, \( |f(x)| \) will mirror it above the x-axis.
- If \( f(x) \) is zero or positive, it remains unchanged.
Linear Functions
Linear functions represent the simplest type of functions that form straight lines when graphed. The general form of a linear function is \( f(x) = ax + b \).
Analyzing their behavior with absolute value transformations can provide valuable insights.
Consider the example \( f(x) = x - 2 \):
Analyzing their behavior with absolute value transformations can provide valuable insights.
Consider the example \( f(x) = x - 2 \):
- The graph crosses the x-axis at \( x = 2 \).
- For \( x < 2 \), the function yields negative values.
- When you apply \( y = |f(x)| \), those negative sections are mirrored upwards, creating a V-like shape.
Quadratic Functions
Quadratic functions are illustrated by parabolas and have the general form \( f(x) = ax^2 + bx + c \).
Their graphs are distinct because of their U-shape or inverted U-shape, depending on the coefficient of the \( x^2 \) term.
Consider \( f(x) = x^2 - 4 \):
Their graphs are distinct because of their U-shape or inverted U-shape, depending on the coefficient of the \( x^2 \) term.
Consider \( f(x) = x^2 - 4 \):
- This quadratic has roots at \( x = -2 \) and \( x=2 \).
- Between these roots, the graph dips below the x-axis.
- With \( y = |f(x)| \), this section flips above, leading to a W-shaped graph.