Quadratic functions are a fundamental part of the study of mathematics, particularly in high school. They are represented by a second-degree polynomial equation, which forms a parabola when graphed.
Understanding the properties of quadratic functions is crucial, as it enables students to analyze their behavior, draw important conclusions, and make predictions.
In this blog, I will dive into the properties of quadratic functions. I will discuss the essential characteristics of a quadratic function, the various forms of a quadratic equation, and how to graph them. If you wonder what is m in y=mx+c? and the role of ‘m’ in linear equations; I encourage you to check out this article.
Essential Characteristics of Quadratic Functions
A quadratic function is a polynomial function of degree two. In simpler terms, it is an algebraic equation with the highest exponent of two that represents a curve. The standard form of a quadratic function is as follows f(x) = ax² + bx + c, where a, b, and c are constants.
The key properties of a quadratic function are the vertex, x-intercepts, and y-intercept.
1- Domain and Range
The domain of a quadratic function is a set of all real numbers, while the range is determined by the value of the leading coefficient. Understanding the domain and range is essential since they help us to predict the behavior of the function beyond the graphed area.
- If the coefficient is positive, the minimum value of the function is the range, and vice versa.
2- Vertex
The vertex is the point at which the function reaches its maximum or minimum value. It is usually represented as (h,k), where h is the x-coordinate, and k is the y-coordinate (Source: University of North Carolina Wilmington)
The vertex provides important information regarding the direction of the parabola and the axis of symmetry. Moreover, it is used to determine the maximum or minimum value of the quadratic function.
- The vertex is the highest or lowest point of the curve, and it occurs at the axis of symmetry.
3- Axis of Symmetry
The axis of symmetry is a vertical line that cuts through the vertex and divides the parabola into two symmetrical halves. It is represented as x=h, where h is the x-coordinate of the vertex.
Knowing the axis of symmetry is critical, especially when graphing a quadratic function, as it simplifies the process and reduces the likelihood of errors.
- The axis of symmetry is a vertical line that divides the curve into two symmetrical halves.
4- X-intercepts and Y-intercepts
The x-intercepts are the points at which the function intersects the x-axis, while the y-intercepts are the points at which the function intersects the y-axis. They are usually represented as (x,y), where x is the x-intercept, and y is the y-intercept.
Knowing the x and y-intercepts enables individuals to identify the exact location of the roots and the starting point of the parabola, respectively.
- The x-intercepts are the points where the curve intersects the x-axis, while the y-intercept is the point where the curve intersects the y-axis.
5- Determining the Transformation of a Quadratic Function
Understanding the transformation of a quadratic function is essential in identifying its equation and predicting its behavior.
The general form of a quadratic function is y=ax2+bx+c, where a,b, and c are constants. Through transformation, the function can be shifted horizontally or vertically, made wider or narrower, or reflected across the x or y-axis.
An accurate understanding of the transformation allows individuals to graph a quadratic function without relying on technology.
Different Forms of Quadratic Equations
There are different forms of quadratic equations, and they all have unique properties. The standard form is ax² + bx + c, as previously mentioned.
- The vertex form is f(x) = a(x-h)² + k, where (h,k) is the vertex of the parabola, and a is the stretch or compression.
- The factored form of a quadratic equation is f(x) = a(x-r₁)(x-r₂), where r₁ and r₂ are the roots or solutions of the equation.
Graphing Quadratic Functions
Graphing a quadratic function involves plotting the vertex and determining the direction of the curve.
- If a > 0, the curve will open upwards.
- And if a < 0, the curve will open downwards. This information is essential when plotting points to sketch the curve.
- You can also use the x-intercepts and y-intercepts to confirm your graph’s accuracy.
Characteristics of Quadratic Functions
A quadratic function’s characteristics can tell you a lot about the equation, even without graphing it. For example:
- If the coefficient ‘a’ is positive, the function will have a minimum value.
- And if ‘a’ is negative, it will have a maximum value.
- We can also determine if the function is even or odd based on its origin.
- Finally, we can determine whether the function is one-to-one and therefore contains an inverse based on the fact that the curve never intersects a horizontal line more than once.
If you want to explore more the properties of quadratic functions in standard form, I invite you to check out Khan Academy or watch the video below.
What to read next:
- Graphing Made Easy: Finding the Easiest Graphing Calculator to Use.
- Finding the Set of Values for Which a Line Does Not Intersect a Curve.
- Types of Math in High School (and everything you must know!)
Final Thoughts
The properties of quadratic functions are essential in analyzing their behavior, determining their features, and making predictions.
I believe that understanding the domain, range, vertex, axis of symmetry, and the x and y-intercepts of a quadratic function provides critical information that can be used to solve problems in various fields, including physics, economics, and engineering.
Moreover, knowing how to transform a quadratic function is crucial for accurate graphing and predictions without access to technology.
In this post, we covered the critical characteristics of quadratic functions, including their different forms and how to graph them. I also believe that knowing these properties can help you identify key aspects of a quadratic equation, which can lead to better analysis and quicker solutions.