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 following Python programming topics:

The standard form of a quadratic equation is:

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

Source Code

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

# import complex math module
import cmath

a = 1
b = 5
c = 6

# To take coefficient input from the users
# a = float(input('Enter a: '))
# b = float(input('Enter b: '))
# c = float(input('Enter c: '))

# 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.