Quadratic Formula Calculator

The quadratic formula calculator is designed to determine the second-order polynomial quadratic equations.

ax2 + bx + c = 0

About Quadratic Formula Calculator

The quadratic formula calculator is a free tool where you can easily solve the quadratic equations. Just enter the three values and get the discriminant, quadratic formula, first root, and second root in an instant.

Quadratic Formula Calculator - Quadratic Equation Solver

What is Quadratic Equation?

The Quadratic name comes from "Quad" and we can also call it "Square" (Like: x2). It's a solution of a second-order polynomial equation with three coefficients.

We can write the equation in standard form like this:

Ax2 + Bx + C = 0 ( Where A ≠ 0 )

Here, A, B, and C are the Coefficients or Known Numbers.

Whereas, the 'x' is the unknown variable that we need to find using the quadratic formula.

The following are some examples for better understanding.

3x2 + 4x + 1 = 0 Here a=3, b=4, and c=1
2x2 - 4x = 0 You can see there is just 2 coefficients values at left side. So, we can figure our the values like this:
  • a = 2
  • b = 4
  • c = 0 (If there is no values then we can consider it 0)
4x + 2 = 0 It is not a quadratic equation. Because there is no x2 value. So, 'a' is counted as 0.

Sometimes the quadratic equations are not in standard form. So, we need to move or expand some coefficients to convert it into standard form.

Let's see some examples:

Disguise Form Rearrangements Standard Form Coefficients
2x2 = 5x - 4 Move right values to left side 2x2 - 5x + 4 = 0 a=2, b=-5, c=4
4(y2 + 3y) = 2 Expand left side and move 2 to left 4y2 + 12y - 2 = 0 a=4, b=12, c=-2

Quadratic Formula

The quadratic formula is as below and it's used to find the "x" value.

Quadratic Formula

Where,

  • a, b, and c are the coefficients. We already have its values.
  • The "Δ" represents the Discriminant. It's used to check the nature of roots.

Δ = b2 - 4ac

Our quadratic formula calculator determines the Discriminant values, whether it is greater than, less than, or equal to 0.

If b2 - 4ac is,

  • Zero, then there is 1 real root.
  • Positive, then there are 2 real root.
  • Negative, then there are 2 complex roots.

How to Solve a Quadratic Equation?

Let's take some examples to understand the process step by step.

Example 1: Solve 2x2 + 5x = -3

Firstly, convert the equation into a standard form like this: ax2 + bx + c = 0.

Take -3 from right to left-hand side. As a result, we get:

2x2 + 5x + 3 = 0

So, we have:

  • a = 2
  • b = 5
  • c = 3

Now place the known values in the quadratic formula.

Quadratic Equation Formula
x =  
-5 ± √(52) - 4(2 × 3)
2 × 2
x =  
-5 ± √25 - 24
4
x =  
-5 ± 1
4

As you can see, the discriminant (b2 - 4ac) = 1 that is > 0. So, there are two real roots.

For the First Root:

x =  
-5 + 1
4

x = -1

For the Second Root:

x =  
-5 - 1
4

x = -1.5

So, the roots of 2x2 + 5x + 3 = 0 are -1 and -1.5.

Example 2: Solve 4x2 + 15x + 20 = 0

Here Coefficients are:

  • a = 4
  • b = 15
  • c = 20

Firstly, let's find the discriminant (Δ):

Δ = b2 − 4ac

= 152 - 4 × (4 × 20)

= 152 - 4 × (80)

= 225 - 320 = -95

Here, the discriminant is -95. That is negative. So, we will get 2 complex roots.

Now let's find the roots.

x =  
-15 ± √(-95)
2 × 4
x =  
-15 ± √(-95)
8

√(-95) = 1.21835i ( Where i = √−1, Imaginary number )

So, x =  
-15 ± 1.21835i
8

Finally, the First Root = -1.875 + 1.21835i and the Second Root = -1.875 - 1.21835i

To solve complex quadratic problems with ease, use our quadratic formula calculator. It will make your calculation easier, faster, and more accurate.

Linear Equation

A linear equation has only one solution or root. In the standard form of quadratic equation, if 'a' becomes 0, then the equation evaluates to bx + c = 0. Hence, it becomes a linear equation. The solution of a linear equation is given by:

  • bx + c = 0
  • bx = -c
  • x = -c/b

Graphical Representation

The graph of a quadratic equation is basically a U-shaped curve called Parabola. The shape of the curve depends upon the sign of 'A' (the coefficient with x2).

  • If a > 0 then the parabola goes up (like a smiley face).
  • If a < 0 then the parabola goes down (like a sad face).

How to Use the Quadratic Formula Calculator?

  1. Firstly, enter the coefficient values (a, b, and c) in the respective input fields.
  2. Now press the Calculate button to get the Discriminant, First root, and Second Root results.
  3. Also, our tool shows the quadratic formula with entered values.
  4. For the new calculations, you can use the Reset button.