I'm not good at math, but I was wondering how to write this difference without wasting 3 pages of my notebook. What do you think?

VibeMathed tracks math problems that AI models have helped prove or disprove, from famous conjectures like the Jacobian conjecture to the numbered Erdős problems at erdosproblems.com. Each entry links a checkable source, carries a verification label (Lean-checked, expert-reviewed, or site-confirmed), and shows a notability score: the number of Wikipedia language editions with a dedicated article, so household names stand out from niche ones.

https://youtube.com/shorts/unPcYziWMYE?feature=share

VibeMathed tracks math problems that AI models have helped prove or disprove, from famous conjectures like the Jacobian conjecture to the numbered Erdős problems at erdosproblems.com. Each entry links a checkable source, carries a verification label (Lean-checked, expert-reviewed, or site-confirmed), and shows a notability score: the number of Wikipedia language editions with a dedicated article, so household names stand out from niche ones.

Hi all,

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I have no idea how well known this is, but I was toying around with the numbers from wikipedia's "divisibility rule" page, like finding what to multiply the last digit by before adding to the rest to find out if a number is divisible by 139 (14 btw) , etc. and I ended up finding out that the number to multiply by seems dependent solely on prime and the last digit of the prime:

end=1: (p*9+1)/10

end=3: (p*3+1)/10

end=7: (p*7+1)/10

end=9: (p*1+1)/10

I even checked much larger primes using terrible python code: (32000167*7+1)/10=22400117, which is the number needed to multiply by... initially because I was trying to find out if any number was multiply by 17 (or certain other numbers) , which there don't seem to be any

Also, x appears to be "circular", sorry if the word is incorrect, but I mean that it works no matter how many times you add or subtract p to/from x, which creates the "subtract y times last from rest", -y=x-p

Closest I could find on the wiki page was under "Divisors Ending in 1, 3, 7, or 9 in base 10", which... might be the same... it's really hard for me to tell... But I could be missing something, even something very obvious, which is why I'm here

A free, open-source tool of step-by-step mathematical proofs. No signup, no ads.

What you can do:

Browse 20 proofs across algebra, calculus, physics, quantum and statistics - quadratic formula, chain rule, finite geometric series, area under the normal curve, Lorentz time dilation, Tsiolkovsky's rocket equation, Bloch sphere parameterization, and others

Step through a proof one line at a time, each step showing its justification

See the region that changed highlighted, so you can spot the actual move instead of diffing two lines of symbols

View the structural graph - the expression parsed into its variables, operators and relationships

Ask questions about a specific step, in context

Derive a new proof from a prompt, optionally attaching your own reference material

View or copy the underlying JSON, or embed a proof elsewhere

Submit your own proof - it goes into a review queue, and you get an edit key to revise it while pending

On the grading. Proofs are AI-generated, and every step is graded by a computer algebra system. The grades are honest about their own limits: a step can come back symbolically proven, or as domain-justified when the CAS can't check it as an identity, or unchecked. Right now about 69% of steps are symbolically established, 25% are domain-justified, and none are refuted. You can see each step's grade and what it means as you go - nothing is hidden behind a "verified" badge.

This is early. 20 proofs is a starting point, not a library, and the repo is growing. That's partly why submissions are open - if there's a derivation you'd like to see in here, send it.

Feedback is welcome, especially on the proofs themselves. If a justification is too thin for a learner, or a step skips something people trip on, that's the most useful thing you can tell me.

https://algebench.org/prove

Been messing around building a little calculator site as a side project (basically teaching myself web dev along the way, so it's held together with duct tape lol). It's got a bunch of percentage/math calculators on it - percentagecalculatornow.com if anyone's curious.

Mostly just wanted to ask this sub since y'all clearly know your math better than me - are there any calculations you find yourself needing that you can never find a good simple tool for? Trying to figure out what's actually useful to add vs what's just noise.

Not trying to sell anything, genuinely just want feedback/ideas from people who'd actually use something like this.

Or do I need to stop reading textbooks while sleep deprived?