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(a) find the zeros algebraically, (b) use a graphing utility to graph the function, and (c) use the graph to approximate any zeros and compare them with those from part (a). \(f(x)=2 x^{4}-2 x^{2}-40\)

Short Answer

Expert verified
The algebraically calculated zeros of the function \(f(x)=2 x^{4}-2 x^{2}-40\) are \(x = -\sqrt{5}, \sqrt{5}, 2i, -2i\). The graphically approximated zeros are similar and are also at \(x = -\sqrt{5}, \sqrt{5}, 2i, -2i\).

Step by step solution

01

Find the zeros algebraically

To find the zeros algebraically, set \(f(x)\) equal to zero and solve for \(x\).\n0 = \(2x^{4}-2x^{2}-40\)\nDivide every term by 2 to simplify, yielding: \n0 = \(x^{4}-x^{2}-20\)\nThen, solve the equation after factoring: \n\(x^{4}-x^{2}-20 = 0\), \((x^{2} - 5)(x^{2} + 4) = 0\)\nSet each factor equal to zero and solve for \(x\) separately: \n\(x^{2} - 5 = 0\), \(x^{2} = 5\). Therefore, \(x = \sqrt{5}\) and \(x = -\sqrt{5}\), \n\(x^{2} + 4 = 0\), \(x^{2} = -4\), therefore, \(x = 2i\) and \(x = -2i\)
02

Graph the function

Next, graph the function \(f(x) = 2x^{4}-2x^{2}-40\) using a graphing utility. Key features to note are the four x-intercepts, which are the zero points of function that align with the zeros calculated in Step 1.
03

Approximate zeros from the graph and compare

From the graph, one can observe that it crosses the x-axis at \(x = -\sqrt{5}, \sqrt{5}\), and is tangent to the x-axis at \(x = 2i, -2i\). The zeros can be approximated visually from the graph. The approximate graphically determined zeros align with the algebraically calculated zeros from Step 1.

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Key Concepts

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

Graphing Polynomial Functions
One of the most effective ways to visualize a polynomial function is through graphing. This allows us to see the overall shape and behavior of the function including its intercepts, turning points, and end behavior. When graphing polynomial functions like the given function, \(f(x) = 2x^{4} - 2x^{2} - 40\), we use graphing utilities or software to generate an accurate curve.

To graph this function manually, however, we would plot a range of x-values and calculate their corresponding y-values, or \(f(x)\) values, to find points on the curve. Important points to identify on the graph are the x-intercepts (also known as zeros), y-intercepts, and the behavior of the graph as x approaches infinity or negative infinity. These features help us understand how the function behaves within the Cartesian plane and provide insights into the nature of its solutions.
Algebraic Solutions to Polynomials
Finding algebraic solutions to polynomials involves locating the values for which the polynomial equals zero. These solutions are also called zeros or roots of the polynomial. In the case of our polynomial function \(f(x)\), we start by setting the function equal to zero and factoring, as illustrated in the step by step solution. Factoring allows us to break down complex polynomials into simpler binomial or trinomial factors that can be easily solved.

In scenarios where factoring is difficult or not possible, other methods such as the Rational Root Theorem, synthetic division, or the use of the quadratic formula may be employed. Identifying the algebraic solutions gives a clear indication of where the function intersects the x-axis or can suggest the presence of complex roots when real solutions are not attainable.
Complex Zeros of Polynomials
Complex zeros occur in polynomial functions when solutions involve imaginary numbers. Imaginary numbers are based on \( \sqrt{-1} \) and are denoted by \( i \). As shown in the exercise, when we factor the polynomial, one of the factors, \(x^{2} + 4\), led to \(x^{2} = -4\), indicating the solutions are \(x = 2i\) and \(x = -2i\).

While these complex solutions do not represent x-intercepts on a traditional two-dimensional graph, they have vital implications in advanced mathematics, including the Fundamental Theorem of Algebra which states that a non-constant polynomial function has as many roots, real or complex, as its degree.
Factoring Polynomials
Factoring is a critical skill when working with polynomials as it helps in breaking down complex equations into simpler parts that are easier to solve. The step by step solution provided shows the factoring of the polynomial \(2x^{4} - 2x^{2} - 40\) into \(x^{4} - x^{2} - 20\), then further into \(x^{2} - 5) (x^{2} + 4\).

To factor effectively, we look for common factors, apply the difference of squares, or use techniques like grouping. Sometimes, when factoring is not straightforward, one might have to apply more advanced methods such as completing the square, using the quadratic formula, or employing numerical methods for higher degree polynomials. Factoring polynomials is foundational in finding both real and complex zeros.

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Most popular questions from this chapter

Find all real zeros of the polynomial function. $$g(x)=4 x^{5}+8 x^{4}-15 x^{3}-23 x^{2}+11 x+15$$

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