Python program to solve quadratic equations

Complete Python examples

When the coefficients a, b and c are known, this program will calculate the roots of the quadratic equation.

To understand this example, you should understand the followingPython programmingTopic:

• 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

Source code

# Solve the quadratic equation ax**2　+　bx　+　c = 0
# Import complex mathematical module
import cmath
a =　1
b =　5
c =　6
# Calculate the discriminant
d = (b**2)　-　(4*a*c)
# Two solutions
sol1　= (-b-cmath.sqrt(d))/(2*a)
sol2　= (-b+cmath.sqrt(d))/(2*a)
print('The solutions are {0} and {1}'.format(sol1,sol2))

Output results

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

We have imported the cmath module for complex square roots. First, we calculate the discriminant, then find the two solutions of the quadratic equation.

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

Complete Python examples