Chapter 2: Problem 63
In Exercises 63-66, use a graphing utility to find the \(x\) -values at which \(f\) is differentiable. \(f(x)=|x+3|\)
Short Answer
Expert verified
The function \(f(x) = |x + 3|\) is differentiable for all \(x\)-values except for \(x = -3\).
Step by step solution
01
Understand the function
The function \(f(x) = |x+3|\) is an absolute value function, which means it will create a 'v' shape in its graphical representation. It will be positive whenever the input, \(x+3\), is positive, and negative whenever \(x+3\) is negative.
02
Identify the critical point
The critical point for the function is when the input to the absolute value operator, \(x+3\), is equal to zero. This is because at this point the function switches from being negative to positive (or vice versa), creating a sharp turn in the graph. This point is what's called 'non-differentiable', meaning there is no derivative at this point. In this case, the critical point is at \(x = -3\).
03
Explain differentiability
A function is differentiable at a particular \(x\)-value if there exists a derivative at that point, meaning the function has a definite slope at that point. In this function, at \(x = -3\), the function does not have a definite slope due to the sharp turn in the graph, thereby making the function non-differentiable at \(x = -3\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Absolute Value Function
An absolute value function is a special type of mathematical function represented as \( f(x) = |x| \). It outputs the non-negative value of any real number \( x \). This simply means that whether you input a positive or negative number, the result will always be positive.
In the exercise given, the function is \( f(x) = |x+3| \). This function will create a graph that looks like a 'V'.
Think of the absolute value as measuring how far a number is from zero on a number line, always yielding a non-negative distance.
The behavior of absolute value graphs is very consistent:
In the exercise given, the function is \( f(x) = |x+3| \). This function will create a graph that looks like a 'V'.
Think of the absolute value as measuring how far a number is from zero on a number line, always yielding a non-negative distance.
The behavior of absolute value graphs is very consistent:
- For inputs where the expression inside the absolute value is positive or zero, \( f(x) = x+3 \).
- For inputs where the expression inside is negative, \( f(x) = -(x+3) \).
Critical Point
A critical point in a function is where the graph changes direction or slope. For absolute value functions, these points often occur where the expression inside the absolute value equals zero.
In \( f(x) = |x+3| \), the critical point is when \( x+3 = 0 \), solving which gives us \( x = -3 \). At this point, the graph switches from decreasing to increasing or vice versa, forming a sharp corner.
It's important to identify critical points as they provide key insights:
In \( f(x) = |x+3| \), the critical point is when \( x+3 = 0 \), solving which gives us \( x = -3 \). At this point, the graph switches from decreasing to increasing or vice versa, forming a sharp corner.
It's important to identify critical points as they provide key insights:
- They indicate where potential changes in direction occur.
- They can highlight areas where the function may be non-differentiable.
Graphing Utility
A graphing utility is a tool that helps visualize functions by plotting their graphs on a coordinate system.
These can be handheld calculators or software applications that provide a graphical representation of functions quickly and accurately.
In the context of \( f(x) = |x+3| \), using a graphing utility will allow you to clearly see the 'V' shape and notice where the critical point \( x = -3 \) causes a sharp turn. This is very helpful for understanding why certain points are non-differentiable.
Benefits of using a graphing utility include:
These can be handheld calculators or software applications that provide a graphical representation of functions quickly and accurately.
In the context of \( f(x) = |x+3| \), using a graphing utility will allow you to clearly see the 'V' shape and notice where the critical point \( x = -3 \) causes a sharp turn. This is very helpful for understanding why certain points are non-differentiable.
Benefits of using a graphing utility include:
- Immediate visualization of complex functions.
- Ability to zoom in on areas of interest, such as critical points.
- Aid in examining the differentiability of functions at various points.
Non-differentiable Points
Non-differentiable points are locations on a graph where a function does not have a derivative.
Simply put, a derivative represents the slope or rate of change at a given point on the graph. If there’s a kink or sharp point—as is often the case with absolute value functions—the derivative doesn't exist.
In \( f(x) = |x+3| \), the graph has a sharp turn at \( x = -3 \), indicating a non-differentiable point. This sharp turn prevents the function from having a single, clear slope, causing the non-differentiable nature at this point.
Key facts about non-differentiable points include:
Simply put, a derivative represents the slope or rate of change at a given point on the graph. If there’s a kink or sharp point—as is often the case with absolute value functions—the derivative doesn't exist.
In \( f(x) = |x+3| \), the graph has a sharp turn at \( x = -3 \), indicating a non-differentiable point. This sharp turn prevents the function from having a single, clear slope, causing the non-differentiable nature at this point.
Key facts about non-differentiable points include:
- They occur generally at sharp edges, cusps, or vertical tangents.
- Functions usually cannot have a defined slope at these points.
- Understanding non-differentiable points helps in knowing where certain rules of calculus do not apply.