Chapter 5: Problem 51
(a) Compare the rates of growth of the functions \(f(x)=2^{x}\) and \(g(x)=x^{5}\) by drawing the graphs of both functions in the following viewing rectangles. (i) \([0,5]\) by \([0,20]\) (ii) \([0,25]\) by \(\left[0,10^{7}\right]\) (iii) \([0,50]\) by \(\left[0,10^{8}\right]\) (b) Find the solutions of the equation \(2^{x}=x^{5},\) correct to one decimal place.
Short Answer
Step by step solution
Understanding the problem
Graphing the functions for (0,5) by (0,20)
Graphing the functions for (0,25) by ([0,10^7])
Graphing the functions for (0,50) by ([0,10^8])
Solving the equation 2^x = x^5
Conclusion
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graphing Functions
Graphing involves selecting a range for both the x-axis (input values) and y-axis (output values). For example, using small increments on the x-axis, such as \([0, 5]\), allows us to see detailed changes in the functions' behavior. As you increase the interval size to \([0,50]\), the graph helps us identify long-term behavior.
- For a small interval \([0, 5]\) and range \([0, 20]\), you might notice \(g(x) = x^5\) initially grows fast, but \(f(x) = 2^x\) overtakes beyond certain points.
- Using larger intervals and ranges allows us to see how quickly \(f(x) = 2^x\) surpasses \(g(x) = x^5\), highlighting the exponential growth's nature.
Rate of Growth Comparison
Exponential functions like \(f(x) = 2^x\) grow proportionally to their current value, meaning growth becomes increasingly rapid as time increases. This characteristic results in a steep rise in the graph, especially visible over larger intervals like \([0, 50]\).
Polynomial functions, such as \(g(x) = x^5\), grow at a slower rate compared to exponential functions as they depend on powers of \(x\). Initially, they may appear to grow quickly in small intervals, but exponential functions eventually outpace them.
- In smaller intervals, like \([0, 5]\), both functions may look competitive with each other.
- As the interval expands to \([0, 50]\), \(f(x) = 2^x\) dominates significantly, illustrating the overarching power of exponential growth.
Numerical Solutions
Why not algebraically? Because exponential and polynomial functions usually don’t intersect in straightforward points; they need approximation.
To solve \(2^x = x^5\), you can:
- Utilize graphing calculators to visually identify approximate points of intersection. This provides a rough estimate.
- Apply numerical methods like the Newton-Raphson method for better precision.
Intersection of Functions
Intersections occur where \(f(x) = g(x)\), represented by their identical outputs on a graph. By examining graphs over different intervals, you can pinpoint these breaks or changes in domination.
For \(f(x) = 2^x\) and \(g(x) = x^5\), their intersections demonstrate key transition points:
- At \(x = 0.0\), both functions start at the same value.
- At approximately \(x = 4.7\), another intersection occurs before \(f(x)\) overtakes permanently.