Discuss a DiscoveR: Possible Number of Local Extrema Is it...

Name: Problem 92, Chapter 3: Precalculus Mathematics for Calculus
Uploaded: 2020-06-10T22:05:29-08:00
Duration: 4 min 13 s
Channel: Aamir Mithaiwala
Description: Discuss a DiscoveR: Possible Number of Local Extrema Is it possible for a third-degree polynomial to have extrema one local extremum? Can a fourth-degree polynomial have exactly two local extrema? How many local extrema can polynomials of third, fourth, fifth, and sixth degree have? (Think about the end behavior of such polynomials.) Now give an example of a polynomial that has six local extrema.

Discuss a DiscoveR: Possible Number of Local Extrema Is it possible for a third-degree polynomial to have extrema one local extremum? Can a fourth-degree polynomial have exactly two local extrema? How many local extrema can polynomials of third, fourth, fifth, and sixth degree have? (Think about the end behavior of such polynomials.) Now give an example of a polynomial that has six local extrema.

Discuss a DiscoveR: Possible Number of Local Extrema
Is it possible for a third-degree polynomial to have extrema
one local extremum? Can a fourth-degree polynomial have
exactly two local extrema? How many local extrema can
polynomials of third, fourth, fifth, and sixth degree have?
(Think about the end behavior of such polynomials.) Now
give an example of a polynomial that has six local extrema.

Key Concepts

Polynomial Degree and Turning Points

The degree of a polynomial sets an upper bound on the number of turning points (or local extrema) that it can have. Specifically, a polynomial of degree n can have at most n-1 turning points. This concept is central in understanding why, for example, a third-degree polynomial cannot have more than two turning points and why a fourth-degree polynomial is limited to at most three turning points, though the actual number of local extrema may be less depending on the specific polynomial.

End Behavior of Polynomials

The end behavior of a polynomial describes how the function behaves as the input grows towards positive or negative infinity, and it is largely determined by the leading term. This characteristic influences the overall shape of the graph and helps in understanding the existence and placement of local extrema. For instance, the way a polynomial’s graph 'opens' up or down informs us about the potential dips and rises that can create local maxima or minima.

Critical Points and Local Extrema

Critical points, which are points where a polynomial’s derivative equals zero or is undefined, are candidates for local extrema. Analyzing these points using tests, such as the first or second derivative test, helps determine whether a point is a local maximum, minimum, or neither. This is a crucial step in understanding and calculating the exact number of local extrema in a polynomial function.

Constructing Specific Polynomial Examples

Creating an example of a polynomial with a specified number of local extrema involves manipulating the polynomial's factors and coefficients to control its turning points. This process requires a deep understanding of both the algebraic structure of polynomials and the geometric implications of their graphs. It is essential for demonstrating theoretical possibilities, such as having a sixth-degree polynomial with up to five turning points, or constructing a polynomial with exactly six local extrema by increasing the degree appropriately.

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