• UnRelatedBurner@sh.itjust.works
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        7 months ago

        Uhm, actually 🤓☝️!

        Afaik sqrt only returns positive numbers, but if you’re searching for X you should do more logic, as both -3 and 3 squared is 9, but sqrt(9) is just 3.

        If I’m wrong please correct me, caz I don’t really know how to properly write this down in a proof, so I might be wrong here. :p
        (ps: I fact checked with wolfram, but I still donno how to split the equation formally)

        • criitz@reddthat.com
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          7 months ago

          You’re correct. The square root operator only returns the principal root (the positive one).

          So if x^2 = 9 then x = ±√9 = ±3

          That’s why in something like the quadratic formula we all had to memorize in school its got a “plus or minus” in it: -b ± √…(etc)

        • h3ndrik@feddit.de
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          7 months ago

          x^2 = 9

          <=>

          |x| = sqrt(9)

          would be correct. That way you get both 3 and -3 for x.

          That’s the way your math teacher would do it. So the correct version of the statement in the picture is: “if x^2 = 9 then abs(x) = 3”