Chapter 5: Problem 54
Graph the polynomial functions using a calculator. Based on the graph, determine the intercepts and the end behavior. $$f(x)=x(14-2 x)(10-2 x)^{2}$$
Short Answer
Expert verified
Intercepts: \((0,0)\), \((7,0)\), \((5,0)\); End behavior: \(f(x) \to \infty\) as \(x \to -\infty\), \(f(x) \to -\infty\) as \(x \to \infty\).
Step by step solution
01
Enter the Function into Calculator
Enter the polynomial function \( f(x) = x(14-2x)(10-2x)^2 \) into your graphing calculator. Make sure you input it correctly to match the expression, including all operations and exponents.
02
Set a Suitable Viewing Window
Adjust the viewing window of your calculator to ensure you can see all relevant features of the graph. This might involve setting the x-range and y-range to values where the graph is clearly visible.
03
Identify the x-Intercepts
Find the points where the graph crosses the x-axis. For \( f(x) = x(14-2x)(10-2x)^2 \), set \( f(x) = 0 \) and solve for \( x \). These solutions include \( x = 0 \), \( x = 7 \), and \( x = 5 \). These values should match the graph's x-intercepts.
04
Determine the y-Intercept
The y-intercept occurs when \( x = 0 \). Substitute \( x = 0 \) into the function to find \( f(0) = 0(14-2\times0)(10-2\times0)^2 = 0 \). So, the y-intercept is \( (0,0) \).
05
Analyze the End Behavior
Examine the behavior of the graph as \( x \) approaches positive and negative infinity. Since \( f(x) = x(14-2x)(10-2x)^2 \) is a third-degree polynomial (degree from the factor \((10-2x)^2\) contributes \( 2 \)), the end behavior is determined by the leading term \(-4x^3\). As \( x \to -\infty \), \( f(x) \to \infty \) and as \( x \to \infty \), \( f(x) \to -\infty \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
graphing calculator
A graphing calculator is a powerful tool that can help us visualize complex equations and functions. It's especially handy when dealing with polynomial functions like the one in our exercise. By plotting the graph of a function, we can easily determine key features such as intercepts and overall behavior. To graph a function with a calculator:
- First, input the entire expression correctly. For the function \( f(x) = x(14-2x)(10-2x)^2 \), ensure each term, multiplication, and power is entered precisely.
- Adjust the viewing window. This often involves setting appropriate ranges for both \( x \) and \( y \)-axes so that you can see the relevant parts of the graph. If the graph appears too small or some intersects aren't visible, tweak these settings accordingly.
x-intercepts
X-intercepts are the points where a function's graph crosses the x-axis. For polynomial functions, these are the real solutions where \( f(x) = 0 \). In mathematical terms, it means finding the roots of the polynomial.
- For the given function \( f(x) = x(14-2x)(10-2x)^2 \), find each factor that equals zero.
- Setting each factor to zero gives the solutions: \( x=0 \), \( x=7 \), and \( x=5 \). These correspond to the x-intercepts.
- Checking with a graphing calculator helps confirm these intercepts visually on the plotted graph.
y-intercepts
The y-intercept of a function is the point where the graph crosses the y-axis, which happens when \( x=0 \). Finding it involves simple substitution into the function.
- For \( f(x) = x(14-2x)(10-2x)^2 \), set \( x = 0 \) and solve for \( f(x) \).
- Calculate as follows: \( f(0) = 0(14-2\times0)(10-2\times0)^2 \), which results in \( f(0)=0 \).
- This tells us the y-intercept is \( (0,0) \).
end behavior
End behavior describes how a function behaves as \( x \) moves towards positive or negative infinity. The degree and leading coefficient of a polynomial help determine this. For a third-degree polynomial like \( f(x) = x(14-2x)(10-2x)^2 \), these aspects are especially informative:
- The function’s leading term, found by multiplying the highest degree terms in each factor, is \( -4x^3 \).
- As \( x \rightarrow -\infty \), the function \( f(x) \rightarrow \infty \).
- As \( x \rightarrow \infty \), the function \( f(x) \rightarrow -\infty \).
third-degree polynomial
A third-degree polynomial, also known as a cubic polynomial, is an expression where the highest power of \( x \) is 3. It typically features a wiggle or wave-like graph owing to its points of inflection and turning points.
- The general form is \( ax^3 + bx^2 + cx + d \), though it can be expressed as a product of its factors.
- In our exercise, \( f(x) = x(14-2x)(10-2x)^2 \) expands to include a degree 3, determined by its terms when fully distributed.
- These polynomials can have up to three real roots and can change direction twice, creating a curve.