Quadratic Expressions
Quadratic expression is an expression with the variable with the highest power of 2. The word quadratic is derived from the word quad which means square. The expression should have the power of two and not higher or lower. Graphically a quadratic expression describes the path followed by a parabola, and it helps in finding the height and time of flight of a rocket.
In this mini-lesson, we will explore the world of quadratic expressions. You will get to learn how to solve quadratic expressions using the discriminant, simplifying quadratic expressions, factorizing expressions, quadratic expressions graphs, and other interesting facts around the topic.
Definition of Quadratic Expressions
An expression of the form ax2 + bx + c, where a ≠ 0 is called a quadratic expression. In other words, any expression with the variables of the highest exponent or the expression's degree as 2 is a quadratic expression The standard form of a quadratic expression looks like this
Here are some examples of expressions:
| Expressions | Values of a, b, and c | |
|---|---|---|
| 1. | 8x2 + 7x - 1 | a = 8 , b = 7 , c = -1 |
| 2. | 4x2 - 9 | a = 4 , b = 0 , c = -9 |
| 3. | x2 + x | a = 1 , b = 1 , c = 0 |
| 4. | 6x - 8 | a = 0 , b = 6 , c = -8 |
Look at example 4, here a = 0. Therefore, it is not a quadratic expression. In fact, this is a linear expression. The remaining expressions are quadratic expression examples. The standard form of the standard expression in variable x is ax2 + bx + c. But always remember that 'a' is a non-zero value and sometimes a quadratic expression is not written in its standard form.
Properties of Quadratic Expression
Listed below are a few important properties to keep in mind while identifying quadratic expressions.
- The expression is usually written in terms of x, y, z, or w. In the alphabets, the letters, in the end, are written for variables whereas the letters, in the beginning, are used for numbers.
- The variable 'a' in a quadratic expression raised to the power of 2 cannot be zero. If a = 0 then x2 will be multiplied by zero and therefore, it would not be a quadratic expression anymore. Variable b or c in the standard form can be 0 but 'a' cannot.
- In a quadratic expression, it is not necessary that all the terms are positive. The standard form is written in a positive form. However, if the numbers are negative the term will also be negative.
- The terms in a quadratic expression are usually written with the power of 2 first, the power of 1 next, and the number in the end.
Ways of Writing a Quadratic Expression
Writing any expression or equation into a quadratic standard form, we need to follow these three methods.
- Move an expression by -1 if the equation starts with a negative value.
- Expand the terms and simply.
- Multiply the factors.
Mentioned below are a few examples:
| Expressions | Steps to Follow | Standard Form |
| (x-1)(x+2) | Multiply the factors (x-1) and (x+2) | x2+ x - 2 |
| -x2+ 3x - 1 | Move expression by -1 | x2 - 3x + 1 |
| 5x(x+3) - 12x | Expand the term 5x(x+3) | 5x2+ 3x |
| x3- x(x2+ x - 3) | Expand the term x(x2 + x - 3) and simplify | x2 - 3x |
Graphing a Quadratic Expressions
The graph of the quadratic expression ax2 + bx + c = 0 can be obtained by representing the quadratic expression as a function y = ax2 + bx + c. Further on solving and substituting values for x, we can obtain values of y, we can obtain numerous points. These points can be presented in the coordinate axis to obtain a parabola-shaped graph for the quadratic expression.
The point where the graph cuts the horizontal x-axis is the solution of the quadratic expression. These points can also be algebraically obtained by equalizing the y value to 0 in the function y = ax2 + bx + c and solving for x. This is how the quadratic expression is represented on a graph. This curve is called a parabola.
Factorizing Quadratic Expressions
The factorizing of a quadratic expression is helpful for splitting it into two simpler expressions, which on multiplying, gives back the original quadratic expression. The aim of factorization is the break down the expression of higher degrees into expressions of lower degrees. Here the quadratic expression is of the second degree and is split into two simple linear expressions. The process of factorization of a quadratic equation includes the first step of splitting the x term, such that the product of the coefficients of the x-term is equal to the constant term. Further, the new expression after splitting the x term has four terms in the quadratic expression. Here some of the terms are taken commonly to obtain the final factors of the quadratic expression. Let us understand the process of factorizing a quadratic expression through an example.
Example 1: 4x - 12x2
Given any quadratic expression, first, check for common factors, i.e. 4x and 12x2
We can observe that 4x is a common factor. Let’s take that common factor from the quadratic expression.
4x - 12x2 = 4x(1 - 3x)
Thus, by simplifying the quadratic expression, we get the expression, 4x - 12x2.
Quadratic Expressions Formula
Solving a quadratic expression is possible if we are able to convert it into a quadratic equation by equalizing it to zero. The values of the variable x which satisfy the quadratic expression and equalize it to zero are called the zeros of the equation. Some of the expressions cannot be easily solved by the method of factorizing. The quadratic formula is here to help. The quadratic formula is also known as "Quadranator." Quadranator alone is enough to solve all quadratic expression problems. The quadratic expressions formula is as follows.
Discriminant
The discriminant is an important part of the quadratic expression formula. The value of the discriminant is (b2 - 4ac). This is called a discriminant because it discriminates the zeroes of the quadratic expression based on its sign. Many an instance we wish to know more about the zeros of the equation, before calculating the roots of the expression. Here the discriminant value is useful. Based on the values of the discriminant the nature of the zeros of the equation or the roots of the equation can be predicted.
The nature of the roots of the quadratic expression based on the discriminant value is as follows.
- When the quadratic expression has two real and distinct roots: b2- 4ac > 0
- When the quadratic expression has equal roots: b2- 4ac = 0
- When the quadratic expression does not have any roots or has imaginary roots: b2- 4ac < 0
Related Topics
The following topics are related to quadratic expressions.
FAQs on Quadratic Expressions
What is a Quadratic Expression in Math?
An expression of the form ax2 + bx + c, where a ≠ 0 is called a quadratic expression in variable x.
What Are the 3 Forms of a Quadratic Expression?
The three forms of quadratic expressions are
- Standard form
- Factored form
- Vertex form
What Does it Mean to Factor a Quadratic Expression?
The factored form of a quadratic expression is to split the quadratic expression into a product of two factors. A quadratic expression is the multiplication of two linear expressions, and the process of factorization is to find the two factors of the quadratic expression..
Which Is a Quadratic Function?
A function of the form f(x) = ax2 + bx + c, where a ≠ 0 is called a quadratic function in variable x. Similar to a function, a quadratic expression also has a domain and a range value.
What Does Quadratic Mean in a Quadratic Expression?
The word "quadratic" is derived from the word "quad" which means square. In the quadratic expression ax2 + bx + c, we have the term x2 which refers to the term quadratic.
How Do you Know If a Polynomial is a Quadratic Expression?
The polynomial expression having a maximum of x2 term is termed as a quadratic expression. The general form of a quadratic expression is ax2 + bx + c, and If the coefficient of x2 is non-zero, then the expression is a quadratic expression.
What Are the Characteristics of a Quadratic Expression?
The characteristics of a quadratic expression are:
- The standard form of the quadratic expression is ax2 + bx + c, where a ≠ 0.
- A quadratic expression has at most two zeroes.
- The curve of the quadratic expression is in the form of a parabola.
What Are the Terms in a Quadratic Expression?
A quadratic expression generally has three terms. The x2 term, the x term, and the constant term. The standard form of a quadratic expression is of the form ax2 + bx + c, and a is a non-zero value. Here a, b are called the coefficients and c is the constant term.
How do you write Quadratic Expressions in Standard Form?
The standard form of a quadratic equation is ax2 + bx + c, where a ≠ 0 in variable x.
How Do you Simplify a Quadratic Expression?
Quadratic equations can be simplified by the process of factorization. Further, the other methods of solving a quadratic equation are by using the formula, and by the method of finding squares. For a quadratic expression of the form x2 + (a + b)x + ab, the process of factorization gives the following simplified factors (x + a)(x + b).