I'm new to Python and I have below this formula and I faced (+/-) before the square root. How could I write it in Python?
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out of the box, you can't. Computer languages and mathematical equations don't always one-to-one. There are two "values/answers" packed in 1 expression here. – Paritosh Singh Aug 03 '19 at 07:37
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This equation is meant to calculate two solutions, you need to find the first using + and the second using - – marc Aug 03 '19 at 07:37
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With array you can – deon cagadoes Aug 03 '19 at 07:38
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1Are you asking what ± means (not a programming question) or how to write corresponding code in Python (in which case, where exactly are you stuck? what have you tried?)? – melpomene Aug 03 '19 at 07:39
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Do you want to print it or evaluate it? – bereal Aug 03 '19 at 07:39
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Check this https://stackoverflow.com/q/27872250/8966274 – Bidhan Majhi Aug 03 '19 at 07:39
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@melpomene I stuck in how to write this (±) in Python? – Aug 03 '19 at 07:43
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@bereal I need to program it in Python – Aug 03 '19 at 07:44
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One way or another, you'll have to build two expressions, one with the plus sign and the other with the minus sign. This is the most straightforward way:
from math import sqrt
x1 = (-b + sqrt(b*b - 4*a*c)) / 2.0
x2 = (-b - sqrt(b*b - 4*a*c)) / 2.0
Of course you should calculate the value of b*b - 4*a*c only once and store it in a variable, and check if it's negative before proceeding (to avoid an error when trying to take the square root of a negative number), but those details are left as an exercise for the reader.
Óscar López
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2That doesn't mean you have to write the same expression twice. You could e.g. `[-b + sign * sqrt(b*b - 4*a*c)) / 2 for sign in [1, -1]]`. – melpomene Aug 03 '19 at 07:42
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@melpomene and more importantly, how do you check if the result is an imaginary number? – Óscar López Aug 03 '19 at 07:46
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@ÓscarLópez I don't understand the question. How do you check it with your code? – melpomene Aug 03 '19 at 07:47
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@melpomene See the comment at the end of my answer. We only need an extra variable, and with that you can check it easily. – Óscar López Aug 03 '19 at 07:48
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@melpomene I'm not asking you. It's just that your proposed solution makes it hard to do the check. – Óscar López Aug 03 '19 at 07:53
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3`D = b*b - 4*a*c; if D < 0: error; [-b + sign * sqrt(D) / 2 for sign in [1, -1]]` – melpomene Aug 03 '19 at 08:00
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This is essentially two formulas represented in one. There is no way to do that in Python. Just use two separate formulas. One with plus one with minus.
Aykhan Hagverdili
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