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In Exercises 51- 54, (a) use a graphing utility to graph the function, (b) use the graph to approximate any \( x \) -intercepts of the graph, (c) set \( y = 0 \) and solve the resulting equation, and (d) compare the results of part (c) with any \( x \) -intercepts of the graph. \( y = \frac{1}{4}x^3(x^2 - 9) \)

Short Answer

Expert verified
The x-intercepts of the function \( y = \frac{1}{4}x^3(x^2 - 9) \) are at \( x = 0 \), \( x = -3 \), and \( x = 3 \).

Step by step solution

01

Graph the function

Use a graphing utility to plot the function \( y = \frac{1}{4}x^3(x^2 - 9) \). The graph will reveal the general behavior of the function.
02

Approximate the x-intercepts

An x-intercept is a point where the graph crosses or touches the x-axis. This is the value of x when y=0. From the graph, identify these points to approximate the x-intercepts.
03

Solve equation for y=0

To find the exact x-intercepts, set \( y = 0 \) in the equation and solve for \( x \). This gives \( 0 = \frac{1}{4}x^3(x^2 - 9) \). Solve the equation by first dividing both sides by \( \frac{1}{4} \), giving \( x^3(x^2 - 9) = 0 \). This equation can be solved by factoring and applying the zero product property. When we factor, we get \( x^3 \times x^2 - x^3 \times 9 = 0 \), or \( x^3x^2 - 9x^3 = 0 \). Finally, set each factor equal to zero and solve for \( x \), yielding the roots \( x = 0 \), \( x = -3 \), and \( x = 3 \).
04

Compare results

The results from part (c) should be consistent with the x-intercepts identified in the graph in step 2. If not, consider possible sources of error. The exact solutions from solving the equation (x = 0, -3, 3) should match with the approximations obtained from the graph.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

x-intercepts
In mathematics, an x-intercept is the point where a graph crosses the x-axis. Essentially, it's the value of \( x \) at which the value of \( y \) becomes zero. Understanding x-intercepts is crucial for solving equations graphically.

To find the x-intercepts, you set the function equal to zero. For example, with the function \( y = \frac{1}{4}x^3(x^2 - 9) \), we can find the x-intercepts by setting \( y = 0 \) and solving for \( x \). This process reveals the points \( x = 0 \), \( x = -3 \), and \( x = 3 \) where the function crosses the x-axis.

Knowing how to locate and interpret x-intercepts helps in graphing functions and understanding their behaviors across different intervals.
Graphing Utility
A graphing utility is a tool that makes plotting functions easier and more accurate. These utilities can be physical calculators or software applications that display graphs based on input equations.

Using a graphing utility with the equation \( y = \frac{1}{4}x^3(x^2 - 9) \), students can visualize how this function behaves. This tool supports understanding by showing the curve, highlighting important features like intercepts and turning points, and aiding in the approximation of x-intercepts. A graphing utility makes it simpler to see where a function intersects the axes and to analyze the function's behavior over a range of x-values.
  • Ensures accurate visualization
  • Helps identify key points like intercepts
  • Makes it easier to understand complex functions
By leveraging these tools, students can confirm their solutions and improve their graph interpretation skills.
Solving Equations
Solving equations is a fundamental skill in math that involves finding all values of variables that satisfy an equation. For the equation \( y = \frac{1}{4}x^3(x^2 - 9) \), solving it means determining when \( y = 0 \), which provides the x-intercepts.

To solve the equation \( 0 = \frac{1}{4}x^3(x^2 - 9) \), the strategy is to factor the equation and apply the zero-product property. This property states that if the product of two factors is zero, at least one of the factors must be zero.

Therefore, solving \( x^3(x^2 - 9) = 0 \) involves finding:\[ x^3 = 0 \] and \[ x^2 - 9 = 0 \].
From \( x^3 = 0 \), we find \( x = 0 \). From \( x^2 - 9 = 0 \), factoring gives \( (x - 3)(x + 3) = 0 \), so \( x = 3 \) and \( x = -3 \). Through solving, these values are confirmed as the x-intercepts, highlighting the consistency between different solution methods.
Factoring Polynomials
Factoring polynomials is an essential algebraic skill used to simplify equations and find their roots. Essentially, factoring aims to represent a polynomial as a product of its factors.

In the equation \( y = \frac{1}{4}x^3(x^2 - 9) \), we factor by first setting aside any common terms or simple factors. Here, factoring involves identifying \( x^3 \) and the difference of squares \( (x^2 - 9) \). This becomes \( x^3(x - 3)(x + 3) \).

When factoring, you break down complex polynomials into simpler components. This step makes solving equations straightforward. The zero-product property allows us to set each factor to zero in turn, thus determining the roots or solutions of the equation.

Mastering polynomial factoring involves recognizing patterns, such as:
  • Common factors
  • Squares differences, such as \( a^2 - b^2 = (a-b)(a+b) \)
  • Simple polynomial products
By honing these skills, students become adept at solving and simplifying polynomial equations, making math problems more manageable.

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