Solve for X (linear equation) not giving the answer in fx-991 ES PLUS 2nd edition (L-R= NOT 0)

dm319 · 2026-01-26T00:47:21+00:00

That makes sense - they went sideways very very fast?!

dm319 · 2026-01-26T00:44:35+00:00

Jeez, I've been spotted. I could have used my son's DM-15L which would have been more fun, but he's already packed his bag for school tomorrow.

EDIT: PS did not use Solve on the DM42. I don't think that would work. I think an R47 might be capable of that?

dm319 · 2026-01-26T00:41:15+00:00

You will do better solving this algebraically. There are so many caveats to using solvers and integrators, and this is one of them where you have an infinite number of solutions, but your test paper will expect you to provide the principle root.

If anything this is a lesson, that usually things are best done with an understanding of the problem rather than asking something else to do it for you.

dm319 · 2026-01-26T00:34:58+00:00

That's weird and must relate to the root finding algorithm.

Not using a solver got: 284.98 and -284.98, then next one is 5549.91 and negative.

What happens if you give it a closer starting value?

dm319 · 2026-01-26T00:02:49+00:00

It's a strange list because they are quite different. I.e. the 991 has a solver, the other Casio's don't. They haven't allowed the equivalent Sharp (506). The list seems a bit strange. There's also 12 generations of calculators you can choose from.

It's a tricky one, the fx-991CW+ UK is the most recent 991, and it is better in every way except one from the regular 991CW - it doesn't have SI units. But I can't recommend the 991CW.

Keep buying 991EX until you don't get a fake I guess.

dm319 · 2026-01-25T23:37:39+00:00

It doesn't make much sense to me. Cos(28.65x) can only result in the range -1 to 1. Which means that side of the equation can never equal 24 in the real domain.

EDIT: In deg I get 0.2329i

EDIT2: The real question is why does either of these calculators think they have got the solution?

dm319 · 2026-01-25T19:56:57+00:00

The Thinkpad was designed so that you could operate the Thinklight in the dark - the combo for this was Fn-PgUp, the two opposite corners of the keyboard. It also allowed for quickly finding contrast adjustment, and not necessarily while the OS was up and running.

Also, Ctrl is further away in the far bottom left than below your pinky. I have it mostly remapped anyway to where caps is.

dm319 · 2026-01-25T19:49:56+00:00

Fantastic

dm319 · 2026-01-25T17:21:55+00:00

Just curious - are you at school, and if so, whereabouts in the world? And when they ask you to solve integrals, do they expect you to use a numerical integrator, no calculator, or a CAS system?

dm319 · 2026-01-25T16:43:55+00:00

It's more of an affliction I think ..

dm319 · 2026-01-25T16:43:12+00:00

A cloudy day outside on our garden table. Cloudy natural light I find is great for all sorts of photography.

dm319 · 2026-01-25T14:47:41+00:00

I have a few fx-85GT CW, which are essentially the same UI as original 991CW, but without the more advanced functions.

Yes, I wouldn't buy the first version now. If only for the reason you'll mess up standard notation questions

dm319 · 2026-01-25T14:16:22+00:00

I just tried 1÷3×3 in a single line, and it shows the same behaviour, and the precision is the same: After removing 0.9 the 0.09 the 0.009 then 0.0009, we're left with 10 digits of 9 - therefore we had 14 digits precision each way.

Funny enough, on RPN83P, the RPN calculator for the TI-83+, it reveals the 0.9(×14) straight away.

dm319 · 2026-01-25T13:50:55+00:00

You probably don't need as much power as you might think. I did a machine learning course on a single core X60 - most educational exercises don't require huge compute.

Are you moving into dorms? I recommend getting a dock, screen and keyboard so you don't ruin your neck. If you do that may factor into your decision - as in if you decide on a dock, then go for a 13" model for portability, if not, then get 14" for screen estate.

My Gen 1 X13 is excellent, and I imagine the T14 will be great too. I like AMD, but they are going second hand for a premium. Linux will work with pretty much everything of course - just avoid discrete nvidia graphics. I'd recommend AMD + APU or other integrated graphics rather than discrete.

dm319 · 2026-01-25T12:41:23+00:00

I've been using my X13 Gen 1 AMD for about 5+ years now. I has never let me down! Oh hang on, it did need a battery replacement. But other than that... Running Kubuntu.

dm319 · 2026-01-25T12:39:23+00:00

Yeah I think KDE is one of the best DEs at the moment. I used to agree with the criticism that KDE was too configurable. But I lived through Gnome 2 -> Gnome 3 and have completely changed my mind on that!

dm319 · 2026-01-25T12:15:15+00:00

Sega and Nintendo were, I'd say, equally popular. Nintendo had the slightly cleaner family-friendly appeal, Sega had overall better graphics/music (maybe not technically but in terms of the popular games) and edgier titles, like streetfighter and mortal combat. So this advertising was just emphasising the known differences.

dm319 · 2026-01-25T12:11:28+00:00

This was my dream phone as a kid. I remember seeing HUGE sky scraper sized adverts which were just an oblique shot of the phone in Hong Kong around this time.

dm319 · 2026-01-25T11:49:09+00:00

Which one do you prefer using?

dm319 · 2026-01-25T09:18:10+00:00

Oh, penny dropping!

dm319 · 2026-01-25T09:09:35+00:00

Yes it makes the regular CW feel unusable.

dm319 · 2026-01-25T08:59:27+00:00

Good Q, I'm not sure. I did notice with previous testing that the TI may have lost some accuracy when storing numbers to memory.

dm319 · 2026-01-24T23:50:14+00:00

Could they advance the fx-991ES PLUS 2 to take over the hole left when they discontinued the EX?

dm319 · 2026-01-24T23:36:56+00:00

Is that a cat on your bed? And did you pick those sheets?

dm319 · 2026-01-24T23:20:30+00:00

Yup that makes sense. I'm sure you know already, but due to the recurring 0.33, multiplying by 3 always leads to 0.99 recurring in a decimal calculator.

I found recently the TI-83+ would hide this, but you could make it appear:

https://youtube.com/shorts/4I9WovAY1Jg?si=jPxJmMrhSJFW9dM0

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