# Python example program to solve the quadratic equation

# Python program to solve the quadratic equation :

In this python programming tutorial, we will learn how to solve a *quadratic equation*. The user will enter the values of the equation, our program will solve it and print out the *result*. The quadratic equation is defined as below :

where, *a,b,* and *c* are *real numbers* and *‘a’* is not equal to *zero*. To find out the value of *x*, we have one equation called *quadratic equation* which is defined as below :

So, if we know the values of *a,b* and *c*, we can find out the value of* ‘x’*. The *‘x’ *will have *two* values or we will have two solutions for any quadratic equation.

### Python program :

#1 import cmath import math #2 a = float(input("Enter the value of a : ")) b = float(input("Enter the value of b : ")) c = float(input("Enter the value of c : ")) #3 d = b**2 - 4*a*c #4 if d < 0 : sol_1 = (-b + cmath.sqrt(d))/2*a sol_2 = (-b - cmath.sqrt(d))/2*a else : sol_1 = (-b + math.sqrt(d))/2*a sol_2 = (-b - math.sqrt(d))/2*a #5 print("The value of x are {} and {}".format(sol_1,sol_2))

### Explanation :

*The commented numbers in the above program denote the step numbers below :*

- We are importing both
*cmath*and*math*modules here. Because the*discriminant*(the part that is under the square root) may or may not be*positive*. If the discriminant is*negative*, the result will contain an*imaginary*part. For negative discriminant, we will use*cmath.sqrt()*, else*math.sqrt()*to find out the square root. - Ask the user to enter the values of
*a,b*and*c*. Read and store them in different variables. - Calculate the
*discriminant*using the user provided values. - Check if the value of the discriminant is
*negative*or not. If yes, use the*cmath.sqrt*, else use*math.sqrt*to find out both solutions. We are storing the solutions in*sol_1*and*sol_2*variables. - Finally, print out the result to the user.

### Sample Output :

Enter the value of a : 1 Enter the value of b : -3 Enter the value of c : -10 The value of x are 5.0 and -2.0 Enter the value of a : 1 Enter the value of b : -18 Enter the value of c : 45 The value of x are 15.0 and 3.0 Enter the value of a : 1 Enter the value of b : 4 Enter the value of c : 5 The value of x are (-2+1j) and (-2-1j)

As you can see, we have two solutions for all three examples. For the first and the second examples, we have *real* solutions and for the third one, we have an *imaginary* solution.

This example is also available on Github.

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