Quadratic equation returns 0 in some cases

Asked May 27 '20 at 12:57

Active May 27 '20 at 12:57

Viewed 46 times

for example when i say x:9 p:3 q:2 it returns x1:(-0-0j) x2:-0-0j. thanks for the help in advanced!

import math, cmath
from math import *
from cmath import *
x = input("input x value:")
pA = input("input p value:")
qA = input("input q value:")

p = int(pA)/int(x)
q = int(qA)/int(x)

solutionA = -(int(p)/2)
solutionB = cmath.sqrt(math.pow((int(p)/2),2)-int(q))
solution1 = solutionA-solutionB
solution2 = solutionA+solutionB

print("x1: {:g}".format(solution1))
print("x2: {:g}".format(solution2))
print ("x1:",solution1)
print ("x2:",solution2)

asked May 27 '20 at 12:57

Lukas Schulte

don't mind the double "print", i just wanted to try different methods – Lukas Schulte May 27 '20 at 12:58
2

Have you considered using `numpy.roots()`? – Eric Jin May 27 '20 at 12:59
1

What exactly is your question here? Zero is, in fact, the result of your expression. With your given inputs, both `p` and `q` are fractions less than 1, so `int(p)` and `int(q)` are both zero. And 0**2-0 is still zero. – jasonharper May 27 '20 at 13:09
1

If you convert a float (e.g. 0.548) to an integer, python will round down. So if p = 3/9, you have the float 0.333, when you later call int(p), you change that into 0. – Kyle Alm May 27 '20 at 13:18
ok, thanks for the good answers – Lukas Schulte May 28 '20 at 08:04
using float() instead of int() worked! thx – Lukas Schulte May 28 '20 at 17:42

Quadratic equation returns 0 in some cases

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