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teachings (mander.xyz)
submitted 5 months ago by [email protected] to c/[email protected]
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[-] [email protected] 50 points 5 months ago* (last edited 5 months ago)

Doesn’t x also equal -3?

[-] [email protected] 91 points 5 months ago

You found the other

[-] [email protected] 3 points 5 months ago

Now kiss

[-] [email protected] 1 points 5 months ago

🎶 I was made for solving you baby 🎶

[-] [email protected] 18 points 5 months ago

Sqrt(9)

[-] [email protected] 29 points 5 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)

[-] [email protected] 25 points 5 months ago* (last edited 5 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)

[-] [email protected] 9 points 5 months ago

Thanks, I haven't connected the dots to that (+-) sign and this problem.

[-] [email protected] 1 points 5 months ago

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...

[-] [email protected] 5 points 5 months ago

I think your calculator is interpreting that as -(3^2) and not (-3)^2

[-] [email protected] 3 points 5 months ago

Oh derp. Yep it is.

Was better when calcs had a +/- button.

And I remembered the math rule too.

[-] [email protected] 1 points 5 months ago

GD I am just realizing how long its been since I did math in my head without a programming language..

I should take a math class again or something and refresh that knowledge.

[-] [email protected] 22 points 5 months ago* (last edited 5 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"

[-] [email protected] 4 points 5 months ago

Cool! Makes sense to me. Honestly, I've never done it this way, but it's so clean. Love it. Thanks.

[-] [email protected] 13 points 5 months ago

Fund the sqrter!

[-] [email protected] 2 points 5 months ago

Sqrt

hehe

this post was submitted on 17 Apr 2024
763 points (98.1% liked)

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