this post was submitted on 15 Aug 2024
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Mitochondria is the power house of the cell (lemm.ee)
submitted 3 months ago* (last edited 3 months ago) by [email protected] to c/[email protected]
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This (arguably unhelpful) phrase seems to be taught across schools all over the world. What are some other phrases like this that are common ?

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[–] [email protected] 10 points 3 months ago (3 children)

To the tune of "Pop Goes The Weasel":

x equals negative b /
plus or minus the square root /
of b squared minus 4 ac /
all over 2a!

I cannot believe that stupid fucking song is still in my head, but good God damn it worked. It's there for all 0 times I'll need the quadratic equation in my daily life.

[–] [email protected] 6 points 3 months ago (2 children)

I can't even visualise what you are saying

[–] [email protected] 10 points 3 months ago

I don't hear it either, though.

[–] [email protected] 4 points 3 months ago (2 children)

I can. But I can't hear it at all.

[–] [email protected] 2 points 3 months ago (2 children)

I know the equation but "hearing" something in your head sounds.. weird

[–] [email protected] 3 points 3 months ago (1 children)

I've been hearing the Donkey Kong song in my head for the last 6 hours. If you know how to make it stop, I'm all ears.

[–] [email protected] 1 points 3 months ago

Things tend to linger when we don't understand them or didn't initially hear them well

We reprocess them until they make sense

[–] [email protected] 1 points 3 months ago

I’ve never seen it with the x equals up front. It works much better when it starts with -b.

[–] [email protected] 3 points 3 months ago

It was to to the tune of Frère Jacques when I learned it. https://en.wikipedia.org/wiki/Fr%C3%A8re_Jacques

Negative b, negative b
Plus or minus square root, plus or minus square root
B squared minus 4 AC, b squared minus 4 AC
Over 2A, over 2A

Finding the name of the original song was a pain. I'd never seen it written as an adult and thought it said "do re mi" so every search result kept telling me it was from the sound of music.

[–] [email protected] 2 points 3 months ago (1 children)

If you already know that much algebra you can use ax2 + bx + c = 0 and solve for x to get the formula if you forget it.

[–] [email protected] 1 points 3 months ago (1 children)

Hurr durr what if I just multiply the whole thing by 4a for some reason? Oh and then after that I'll add b² to both sides, just for shits and giggles. And for good measure, I'll move a few numbers from one side to the other, and that leaves me with 4a²x² + 4abx + b² = b² - 4ac.

And then golly gee! Wouldn't you know it? That just happens to let the left side factor neatly into (2ax + b)²! So I'll just take the square root of both sides...

No!

No!

Bad!

This is fucking voodoo. I hate this shit. It's like trigonometric substitution.

Math is procedural. Math is algorithmic. Math is repeatable.

"If these numbers looked a little different than they do, I could solve this. Oh, wow! If I just sprinkle these magic values into my problem, everything works out great!"

Oh yes, I can see how if you just plug in this shit you pulled out of your ass, everything works out great! But when you aren't around for a fecal transfer, I have no idea how to come up with that.

I was top of my class in math. But that voodoo shit never made any sense to me.

And there is absolute value of zero chance I could figure all that out in the heat of the moment if I forgot the quadratic formula. I had to work backwards from the formula to even get all that in the first place.

[–] [email protected] 3 points 3 months ago (1 children)
  • ax^2 + bx + c = 0
  • ax^2 + bx = -c move the c over
  • x^2 + (b/a)x = -c/a divide by a
  • x^2 + (b/a)x +(b/2a)^2 = -c/a + (b/2a)^2 complete the square
  • (x + b/2a)^2 = -c/a + (b/2a)^2 factor the left hand side
  • x + b/2a = sqrt(-c/a + (b/2a)^2) now we just tidy it up
  • x = -b/2a + sqrt(-c/a + b^2/4a^2)
  • x = -b/2a + (2a/2a) sqrt(-c/a + b^2/4a^2)
  • x = (-b + (2a)sqrt(-c/a + b^2/4a^2))/2a
  • x = (-b + sqrt(-4ac + b^2))/2a move 2a into the square root and multiply it with what's inside

The derivation of the quadratic formula is nice because it doesn't rely on anything fancy and it's all tricks the teacher is likely to teach around the same time you're learning it. It's not voodoo shit, it's just the ax^2 + bx + c = 0 and you solve for x.

[–] [email protected] 1 points 3 months ago

Thanks for the alternative explanation. Completing the square never made much sense to me either, so I never would have arrived there.