Python Program to Solve Quadratic Equation

This program computes roots of a quadratic equation when coefficients a, b and c are known.

To understand this example, you should have the knowledge of the following Python programming topics:

• Python Data Types
• Python Input, Output and Import
• Python Operators

The standard form of a quadratic equation is:

ax2 + bx + c = 0, where
a, b and c are real numbers and
a ≠ 0

The solutions of this quadratic equation is given by:

(-b ± (b ** 2 - 4 * a * c) ** 0.5) / 2 * a

Source Code

# Solve the quadratic equation ax**2 + bx + c = 0

# import complex math module
import cmath

a = 1
b = 5
c = 6

# calculate the discriminant
d = (b**2) - (4*a*c)

# find two solutions
sol1 = (-b-cmath.sqrt(d))/(2*a)
sol2 = (-b+cmath.sqrt(d))/(2*a)

print('The solution are {0} and {1}'.format(sol1,sol2))

Output

Enter a: 1
Enter b: 5
Enter c: 6
The solutions are (-3+0j) and (-2+0j)

We have imported the cmath module to perform complex square root. First, we calculate the discriminant and then find the two solutions of the quadratic equation.

You can change the value of a, b and c in the above program and test this program.