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How do you input a plus-minus sign into Wolfram Alpha?

Posted 10 years ago
I have trouble trying to input anything that requires a plus-minus sign:
e.g.
"x ± 1 = n^2" returns nothing.
"x plus-minus 1  = n^2" returns nothing.
"x plus or minus 1 = n^2" returns nothing.

The extended keyboard also doesn't help, because the plus-minus sign doesn't show up there either.
I tried copying the sign from formulas that use the plus-minus sign (e.g. the quadratic formula, etc.), but it refuses to input the whole formula, instead asking me to purchase Pro subscription to use Input Zoom on the quadratic formula etc. Absurd, isn't it?
4 Replies

Actually, they have a feature for this now - it's "PlusMinus[x]"!

  • Say you want "y = 2x ± 5" - put in "y = 2x PlusMinus[5]"!
  • If you want "y = 2x ±(5+7+9)" - put in "y = 2x PlusMinus[5+7+9]"!
POSTED BY: Paintspot Infez
There is no mathematical operation called plus/minus, the foundational axioms and theorems of algebra don't allow it.  The plus/minus as you describe it is a type set.  However, it is easy to operate with it, by setting up the equations seperaty as a list.  Using Solve[ ] to solve a quadratic equation with give the plus/minus solutions as a list; try it.  From your example: x + 1 == n^2 and x - 1 == n^2  expresses the equations. Example:  Solve[{x + 13 == 25, x - 13 ==25}, x] works in Mathematica.
POSTED BY: Daniel Sanders
Mathematica itself doesn't have an operator like plus-minus and I don't believe that Wolfram|Alpha does either. It's an interesting idea - I hadn't considered it until now.

So I think the short answer is that Wolfram|Alpha won't interpret the +/- character as you probably intend it to.  The best thing you can do is run the query once with plus and once with minus. 

If you think this would be a good addition onto Wolfram|Alpha, let them know in the comment box at the bottom of the page which shows the results of your query to Wolfram|Alpha.
POSTED BY: Sean Clarke
Just like Jeopardy, you have to "buy a plus sign,"
POSTED BY: S M Blinder
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