25 points
*
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)
9 points
1 point
So I checked this on my smartphone first, and thought maybe the software is just shit… So then I checked it on a Casio scientific calc, and both agree.
-3^2 = -9… And 9 != -9
… Are all the calculators somehow wrong? What’s the math rule I’m forgetting here…
5 points
3 points
Oh derp. Yep it is.
Was better when calcs had a +/- button.
And I remembered the math rule too.
