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Ch. 3 - Polynomial and Rational Functions
Lial - College Algebra 13th Edition
Lial13th EditionCollege AlgebraISBN: 9780136881063Not the one you use?Change textbook
Chapter 4, Problem 5

Determine whether each statement is true or false. If false, explain why. A polynomial function having degree 6 and only real coefficients may have no real zeros.

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Recall the Fundamental Theorem of Algebra, which states that a polynomial of degree \(n\) has exactly \(n\) roots (zeros) in the complex number system, counting multiplicities.
Since the polynomial has degree 6, it must have exactly 6 roots in total, but these roots can be real or complex.
Because the polynomial has only real coefficients, any non-real complex roots must occur in conjugate pairs. This means complex roots come in pairs like \(a + bi\) and \(a - bi\).
If the polynomial had no real zeros, then all 6 roots would be complex and must come in conjugate pairs. Since 6 is even, it is possible to have 3 pairs of complex conjugate roots and no real roots.
Therefore, it is possible for a degree 6 polynomial with real coefficients to have no real zeros, making the statement true.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Polynomial Degree and Zeros

The degree of a polynomial indicates the highest power of the variable and determines the maximum number of zeros (roots) the polynomial can have. A polynomial of degree 6 can have up to 6 zeros, counting multiplicities and including complex zeros.
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Real and Complex Zeros

Polynomials with real coefficients may have zeros that are real or complex. Complex zeros occur in conjugate pairs, meaning if a + bi is a zero, then a - bi is also a zero. This ensures the polynomial's coefficients remain real.
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Fundamental Theorem of Algebra

This theorem states that every non-constant polynomial has at least one complex root. For polynomials with real coefficients, all roots (real or complex) sum to the degree of the polynomial, but it is possible for a polynomial to have no real roots if all zeros are complex conjugates.
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