Chapter 4: Problem 44
\(37-50=\) Find the absolute maximum and absolute minimum values of \(f\) on the given interval. $$f(x)=\frac{x}{x^{2}-x+1},[0,3]$$
Short Answer
Expert verified
Maximum is 1 at \(x=1\), minimum is 0 at \(x=0\).
Step by step solution
01
Identify critical points of \(f\)
To find the critical points, we first need to find the derivative of the function \(f(x) = \frac{x}{x^{2}-x+1}\). Using the quotient rule, we have:\[f'(x) = \frac{(1)(x^2 - x + 1) - x(2x - 1)}{(x^2-x+1)^2}\]Simplifying this:\[f'(x) = \frac{x^2 - x + 1 - 2x^2 + x}{(x^2 - x + 1)^2} = \frac{-x^2 + 1}{(x^2 - x + 1)^2}\]Setting \(f'(x) = 0\) gives us the critical points by solving \(-x^2 + 1 = 0\), leading to \(x = \pm 1\). Only \(x = 1\) is in the interval \([0, 3]\).
02
Evaluate \(f(x)\) at critical points and endpoints
Now that we have the critical point \(x=1\), we must evaluate \(f(x)\) at this point and the endpoints of the interval \([0, 3]\).- At \(x = 0\):\[f(0) = \frac{0}{0^2 - 0 + 1} = 0\]- At \(x = 1\):\[f(1) = \frac{1}{1^2 - 1 + 1} = 1\]- At \(x = 3\):\[f(3) = \frac{3}{3^2 - 3 + 1} = \frac{3}{7}\]
03
Determine absolute maximum and minimum values
Compare the function values obtained in Step 2:- \(f(0) = 0\)- \(f(1) = 1\)- \(f(3) = \frac{3}{7}\)The absolute maximum value is \(f(1) = 1\) and the absolute minimum value is \(f(0) = 0\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Critical Points
In calculus, critical points are essential for identifying where a function might achieve its local maxima or minima. These are points where the derivative of a function either equals zero or does not exist. When working with a function like \(f(x)\), finding these points is an important step in optimization problems. Here is how you find them:
- First, compute the derivative of the function. For a function \(f(x)\), you're looking for \(f'(x)\).
- Next, solve \(f'(x) = 0\) to find values of \(x\) where the slope of the tangent is zero.
- Consider also where \(f'(x)\) might not exist, which could also indicate potential critical points.
Derivative
The derivative is a core concept in calculus, often called the rate of change of a function. When solving problems involving optimization, the derivative helps us understand how a function behaves. To find a derivative like in this exercise:
- Use rules such as the quotient rule if dealing with a fraction as \(f(x) = \frac{x}{x^2 - x + 1}\).
- The quotient rule states: If \(f(x) = \frac{u(x)}{v(x)}\), then \(f'(x) = \frac{u'(x)v(x) - u(x)v'(x)}{v(x)^2}\).
- Apply this rule to get \[f'(x) = \frac{(1)(x^2 - x + 1) - x(2x - 1)}{(x^2-x+1)^2}\].
Absolute Maximum and Minimum
Identifying the absolute maximum and minimum values of a function in a defined interval is the core goal of an optimization problem. Here’s how it’s typically done:
- Find the critical points of the function within the interval, which we did through the derivative \(f'(x)\).
- Evaluate the original function, \(f(x)\), at these critical points and at the endpoints of the interval. This ensures that potential maxima or minima aren’t missed.
- Compare these function values. The largest value is the absolute maximum, and the smallest is the absolute minimum.