Chapter 2: Problem 73
Determine the point(s) at which the graph of the function has a horizontal tangent line. \(f(x)=\frac{x^{2}}{x-1}\)
Short Answer
Expert verified
The function \(f(x) = \frac{x^{2}}{x-1}\) has horizontal tangents at \(x = 0\) and \(x = 2\).
Step by step solution
01
Compute the Derivative
First need to compute the derivative of the given function, using the quotient rule which is \((\frac{u}{v})'=\frac{u'v-uv'}{v^{2}}\). Here \(u = x^2\) and \(v = x - 1\), so compute \(u'\) and \(v'\) first. \(u'= 2x\) and \(v' = 1\). Now we can compute the derivative: \(f'(x)=\frac{(2x)(x - 1) - (x^2)(1)}{(x - 1)^2} = \frac{2x^2 - 2x - x^2}{(x - 1)^2} = \frac{x^2 - 2x}{(x - 1)^2}\).
02
Find Where the Derivative Equals 0
Now to find the x-values for which the derivative is 0, meaning \(\frac{x^2 - 2x}{(x - 1)^2} = 0\). The numerator of a fraction must equal 0 for the entire fraction to be 0, so this simplifies to finding the roots of the equation \(x^2 - 2x = 0\).
03
Solve the Quadratic Equation
Now need to solve \(x^2 - 2x = 0\). This is a simple quadratic equation, which can be factored to \(x(x - 2) = 0\). Setting each factor equal to 0 gives the possible solutions \(x = 0\) and \(x = 2\).
04
Check the Validity of the Solutions
The potential solutions \(x = 0\) and \(x = 2\) must be checked against the domain of the original f(x) function. However, the function is undefined at \(x = 1\), but is defined everywhere else including our solutions.
05
Final Answer
The function \(f(x) = \frac{x^{2}}{x-1}\) has horizontal tangent lines at \(x = 0\) and \(x = 2\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Derivatives
Derivatives are a fundamental concept in calculus. They measure how a function changes as its input changes. Think of it as the rate of change or the slope of a function at a given point.
For a function \( f(x) \), the derivative \( f'(x) \) gives the slope of the tangent line at any point \( x \). This is crucial for understanding how the function behaves locally.
For a function \( f(x) \), the derivative \( f'(x) \) gives the slope of the tangent line at any point \( x \). This is crucial for understanding how the function behaves locally.
- To compute a derivative, you need to apply specific rules, depending on the function's form.
- Common rules include the power rule, product rule, quotient rule, and chain rule.
Finding Horizontal Tangent Lines
A horizontal tangent line occurs at points where the derivative of a function is zero. This means there's no slope at that point—the graph is flat like a horizontal line.
Why is this important? Horizontal tangents indicate peaks, troughs, or level sections of the graph, helping us understand the behavior of the function:
Why is this important? Horizontal tangents indicate peaks, troughs, or level sections of the graph, helping us understand the behavior of the function:
- Solving \( f'(x) = 0 \) will give the x-values where the graph has horizontal tangents.
- These x-values often show where a function changes direction.
Applying the Quotient Rule
The quotient rule is used to find the derivative of a quotient or division of two functions. If you have a function \( f(x) = \frac{u(x)}{v(x)} \), the quotient rule states that:\[ \left(\frac{u}{v}\right)' = \frac{u'v - uv'}{v^2} \]Here's how you can break it down:
- Identify the top and bottom functions: \( u(x) \) and \( v(x) \).
- Find their derivatives: \( u'(x) \) and \( v'(x) \).
- Plug these into the formula.
Solving Quadratic Equations
Quadratic equations appear frequently in mathematics and are typically in the form \( ax^2 + bx + c = 0 \). The solutions are the x-values where the equation is true.
To solve these, you can:
To solve these, you can:
- Factor the equation if possible, by finding numbers that multiply to \( ac \) and add to \( b \).
- Use the quadratic formula: \( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \).
- Complete the square, if necessary.