Summary: Graphs of Polynomial Functions

Key Concepts

Polynomial functions of degree 2 or more are smooth, continuous functions.
To find the zeros of a polynomial function, if it can be factored, factor the function and set each factor equal to zero.
Another way to find the x-intercepts of a polynomial function is to graph the function and identify the points where the graph crosses the x-axis.
The multiplicity of a zero determines how the graph behaves at the x-intercept.
The graph of a polynomial will cross the x-axis at a zero with odd multiplicity.
The graph of a polynomial will touch and bounce off the x-axis at a zero with even multiplicity.
The end behavior of a polynomial function depends on the leading term.
The graph of a polynomial function changes direction at its turning points.
A polynomial function of degree n has at most n – 1 turning points.
To graph polynomial functions, find the zeros and their multiplicities, determine the end behavior, and ensure that the final graph has at most n – 1 turning points.
Graphing a polynomial function helps to estimate local and global extremas.
The Intermediate Value Theorem tells us that if $f\left(a\right) \text{and} f\left(b\right)$ have opposite signs, then there exists at least one value c between a and b for which $f\left(c\right)=0$ .

global maximum: highest turning point on a graph; $f\left(a\right)$ where $f\left(a\right)\ge f\left(x\right)$ for all x.

global minimum: lowest turning point on a graph; $f\left(a\right)$ where $f\left(a\right)\le f\left(x\right)$ for all x.

Intermediate Value Theorem: for two numbers a and b in the domain of f, if [latex]af takes on every value between $f\left(a\right)$ and $f\left(b\right)$ ; specifically, when a polynomial function changes from a negative value to a positive value, the function must cross the x-axis

multiplicity: the number of times a given factor appears in the factored form of the equation of a polynomial; if a polynomial contains a factor of the form ${\left(x-h\right)}^{p}$ , $x=h$ is a zero of multiplicity p.