Question

Rule book:

1.)Must be Python -

2.) no imported module (ie cmath) - no can do on the imports... pure code..

3.) numbers are float - not integer.

Here's the prompt:

(Algebra: solve quadratic equations)

The two roots of a quadratic equation ax^2 + bx + c = 0 can be obtained using the following formula:

r1 = (-b + sqrt(b^2 - 4ac)) / (2a)

and

r2 = (-b - sqrt(b^2 - 4ac)) / (2a)

b^2 - 4ac is called the discriminant of the quadratic equation. If it is positive, the equation has two real roots. If it is zero, the equation has one root. If it is negative, the equation has no real roots.

Write a program that prompts the user to enter values for a, b, and c and displays the result based on the discriminant.

If the discriminant is positive, display two roots.

If the discriminant is 0, display one root.

Otherwise, display “The equation has no real roots”.

Sample Run 1

Enter a: 1.0

Enter b: 3

Enter c: 1

The roots are -0.3819660112501051 and -2.618033988749895

Sample Run 2

Enter a: 1

Enter b: 2.0

Enter c: 1

The root is -1.0

Sample Run 3

Enter a: 1

Enter b: 2

Enter c: 3

The equation has no real roots

----------------------------------------------------------------------------------End of Prompt---------------------

For the sample run above... 1.0, 2 and 3

Here's my code (one of several variants): I'm close...my code produces roots of 2.45 and 3.54... but no cigar....maybe order of operations error?.. the solution is supposed to be -0.3819660112501051 and -2.618033988749895

Code below...

And... reminder... inputs are 1.0, 3 and 1, float values for inputs and no math modules - just code

#step one, have the user input values
a = float(input('Enter a value for a: '))
b = float(input('Enter a value for b: '))
c = float(input('Enter a value for c: '))

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

print('the discriminant is ',discriminant)
discRoot = discriminant ** (.05)
print('this is the square root of the discriminant ',discRoot)

if discriminant > 0:
print(f'The discriminant {discriminant} is\
greater than zero, so there are two roots.')
#calculate root1
root1 = (-b + (discRoot /2*a))
print(f'the first root is {root1}')
#calculate root2
root2 = (-b - (discRoot /2*a) )
print(f'the second root is {root2}')
elif discriminant == 0:
print(f'The discriminant {discriminant} is zero, so there is one root')
else:
print(f'The discriminant is: {discriminant}, so the\
equation has no real roots')

Big thanks to the wizard who can help me out. ;)

Answer 1

Here is the corrected code for this problem. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks

Note: I have also modified the output format to fit the expected output as sample runs

#code

#step one, have the user input values
a = float(input('Enter a value for a: '))
b = float(input('Enter a value for b: '))
c = float(input('Enter a value for c: '))

# calculate the discriminant
discriminant = (b*b - 4*a*c)
#to find square root, you should use **(.5) instead of **(.05)
discRoot = discriminant ** (.5)

if discriminant > 0:
    #two roots exist
    #calculate root1
  root1 = ((-b + discRoot) /2*a) #the brackets were wrongly put before
    #calculate root2
    root2 = ((-b - discRoot) /2*a)
    #printing the two roots
    print(f'The roots are {root1} and {root2}')
elif discriminant == 0:
    #one single root exist
    root = (-b / 2 * a)
    #printing the single root
    print(f'The root is {root}')
else:
    #no roots
    print('The equation has no real roots')

#output (multiple runs)

Enter a value for a: 1

Enter a value for b: 3

Enter a value for c: 1

The roots are -0.3819660112501051 and -2.618033988749895





Enter a value for a: 1

Enter a value for b: 2

Enter a value for c: 1

The root is -1.0

Enter a value for a: 1

Enter a value for b: 2

Enter a value for c: 3

The equation has no real roots