Grade 11 → Functions and Graphs → Types of Functions ↓
Polynomial Functions
Polynomial functions are a class of mathematical functions that are algebraic expressions. Understanding polynomial functions is essential because they form the basic structure of various mathematical modeling processes. They appear in many real-world scenarios and are the building blocks of many more complex functions found in mathematics.
What are polynomial functions?
A polynomial function is a function that can be represented in the following general form:
f(x) = a n x n + a n-1 x n-1 + ... + a 1 x + a 0
Here, a n , a n-1 , ..., a 0
are constants known as the coefficients of the polynomial, and n
is a non-negative integer known as the degree of the polynomial. The highest power of x
(which is n
in a n x n
) is the degree of the polynomial. The term a n
must not be zero for n
to be a degree.
Types of polynomial functions
Polynomial functions come in different forms depending on their degree:
- Stable functions:
A polynomial function with degree 0. For example,f(x) = 7
The graph of a constant function is a horizontal line.f(x) = c
- Linear function:
A polynomial function with degree 1. For example,f(x) = 2x + 3
Linear functions graph as straight lines.f(x) = mx + c
- Quadratic function:
A polynomial function with degree 2. For example,f(x) = x 2 - 4x + 4
graphs a quadratic as a parabola.f(x) = ax 2 + bx + c
- Cube function:
A polynomial function with degree 3. For example,f(x) = x 3 - 3x 2 + x - 2
Cubic functions show more complexities and many twists.f(x) = ax 3 + bx 2 + cx + d
- Quartile function:
A polynomial with degree 4, such asf(x) = x 4 - 2x 2 + 1
can produce graphs that appear wavy or U-shaped.f(x) = ax 4 + bx 3 + cx 2 + dx + e
Graphing polynomial functions
Graphing polynomial functions helps to see the roots and behaviour of the function. Some important features to note while plotting the graph are as follows:
- Interception:
- Y-intercept: The point where the graph crosses the y-axis. Found by evaluating f(0).
- X-intercepts (origins): The points where the graph crosses or touches the x-axis, found by solving
f(x) = 0
.
- End Behavior:
- Determined by the leading term (highest power term) of the polynomial.
- If the degree is even, both ends will go in the same direction, up if the leading coefficient is positive, and down if it is negative.
- If the degree is odd, the ends move in opposite directions, shifting up to the right for a positive leading coefficient and down to the right for a negative leading coefficient.
- Turning Point:
- The maximum number of turning points is
n-1
, wheren
is the degree of the polynomial.
- The maximum number of turning points is
Examples of polynomial functions
Let's look at some examples and learn how to identify the degree, leading coefficient, and graph a polynomial:
Example 1: Quadratic polynomial
Given: f(x) = x 2 - 3x + 2
- Degree: 2 (quadratic)
- Leading coefficient: 1
- Y-intercept: f(0) = 2
- X-intercept: Solving for
x 2 - 3x + 2 = 0
gives the rootsx = 1
andx = 2
Example 2: Cubic polynomial
Given: f(x) = x 3 - 4x
- Degree: 3 (cubic)
- Leading coefficient: 1
- Y-intercept: f(0) = 0
- X-intercept: Solving for
x 3 - 4x = 0
gives roots atx = 0
,x = 2
, andx = -2
Properties of polynomial functions
When dealing with polynomial functions, there are several inherent properties:
- Continuous and Smooth: Polynomial functions are continuous everywhere. This means that the graph has no breaks, jumps, or sharp edges.
- Factorable: any polynomial can be factored into linear factors (may involve complex or imaginary numbers for some roots).
- Maximum degree: The number of x-intercepts and local maximums/minimums is finite compared to the degree.
Applications of polynomial functions
Polynomial functions are widely used in various fields:
- Physics: Polynomial functions represent the motion of objects where the acceleration remains constant.
- Economics: Used to prepare cost, revenue, and profit models.
- Engineering: modeling of loads and forces, as well as the analysis of structures and systems.
- Biology: Study of population growth rates and various biological systems.
Conclusion
Polynomial functions are fundamental in mathematics and science. Understanding their structure, types, graphing methods, and applications not only enhances problem-solving skills but also provides a foundation for studying more complex equations and functions in advanced mathematics. Whether you are predicting the behavior of a physical system or analyzing complex data trends, polynomial functions serve as invaluable tools in your mathematical toolkit.