Python Help making quadratic formula in python

[Python] Help making quadratic formula in python - Printable Version

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Help making quadratic formula in python - Gerymc - Jul 2, 2017

I am trying to make a program in which you enter the A, B, and C variables in the quadratic formula and it find's X's two values. I already set up an if-else statement so that if the discriminant is negative, it will tell the user there are no solutions, however I am having trouble on the actual math part.

The quadratic formula is x = -b±√b^2-4ac all divided by 2a.

Part of my code is below. As you can see in the else statement, I set up two variables because X can have two different answers because there is the plus-minus sign. Would the way I did it be the correct way to do it? When I try to test it out, it gives the wrong answers so my math is wrong somehow.

Code 
#Makes a variable for the discriminant

    disc = b**2 - 4*a*c

#If the discriminant is less than 0, it says no real solutions

    if disc < 0:

        print "No real solutions"

#If the discriminant is 0, it finds the 1 value of X

    elif disc == 0:

        x = -b+((b**2 - 4*a*c)**.5)/2*a

        print "x = " + str(x)

    else:

        x1 = -b+((b**2 - 4*a*c)**.5)/2*a

        x2 = -b-((b**2 - 4*a*c)**.5)/2*a

        print "x = " + str(x1) + str(x2)

EDIT: Realized that I need to make the formula like this:

Code 
(-b+((b**2 - 4*a*c)**.5))/2*a

* - slober - Jul 2, 2017

You can write it a bit shorter if you wanted to.
ex.

Code 
import cmath

delta = (b**2) - (4*a*c)

solution1 = (-b-cmath.sqrt(delta))/(2*a)

solution2 = (-b+cmath.sqrt(delta))/(2*a)

* - Gerymc - Jul 2, 2017

(Jul 2, 2017 01:37 PM)slober Wrote: You can write it a bit shorter if you wanted to.
ex.

Code
import cmath delta = (b**2) - (4*a*c) solution1 = (-b-cmath.sqrt(delta))/(2*a) solution2 = (-b+cmath.sqrt(delta))/(2*a)

I'm doing this for a class and they didn't teach us that yet, so I can't use it.

* - slober - Jul 2, 2017

(Jul 2, 2017 01:41 PM)jdugerymc Wrote: I'm doing this for a class and they didn't teach us that yet, so I can't use it.

This would be my full solution

Code 
import cmath

print('Solve the quadratic equation: ax**2 + bx + c = 0')

a = float(input('Please enter a : '))

b = float(input('Please enter b : '))

c = float(input('Please enter c : '))

delta = (b**2) - (4*a*c)

if delta < 0:

    print ("No real solutions")

elif delta == 0:

    solution1 = (-b+cmath.sqrt(delta))/(2*a)

    print ('x =',solution1)

else:

    solution1 = (-b-cmath.sqrt(delta))/(2*a)

    solution2 = (-b+cmath.sqrt(delta))/(2*a)

    print ('x =',solution1)

    print('x =',solution2)

Code 
print ('x1 = {0} and x2 {1}'.format(solution1,solution2))

What kind of class are you following?

* - Gerymc - Jul 2, 2017

(Jul 2, 2017 01:54 PM)slober Wrote: This would be my full solution

Code
import cmath print('Solve the quadratic equation: ax**2 + bx + c = 0') a = float(input('Please enter a : ')) b = float(input('Please enter b : ')) c = float(input('Please enter c : ')) delta = (b**2) - (4*a*c) if delta < 0: print ("No real solutions") elif delta == 0: solution1 = (-b+cmath.sqrt(delta))/(2*a) print ('x =',solution1) else: solution1 = (-b-cmath.sqrt(delta))/(2*a) solution2 = (-b+cmath.sqrt(delta))/(2*a) print ('x =',solution1) print('x =',solution2)

What kind of class are you following?

It is just a summer class "Computational Thinking Part 1" I believe. It is a prerequisite for other computer science classes.

But I already fixed it, thanks for the help though. I forgot to add some parentheses.

* - arkoydas - Jul 3, 2017

Is there any way to do it fast with list comprehension?