Casio FX-115MS bug
10-31-2018, 07:02 PM (This post was last modified: 09-10-2019 04:54 PM by Albert Chan.)
Post: #1
 Albert Chan Senior Member Posts: 695 Joined: Jul 2018
Casio FX-115MS bug
Tried solving a cubic using Casio FX-115MS:

1295/24 X³ - 1295/12 X² - 37/2 X + 0.248048 = 0

The calculator just crashed, with weird blinking random pixels ...

Same cubic, but scaled, avoided the crash:

f(X) = 1295 X³ - 2590 X² - 444 X + 5.953152 = 0

--> 3 roots = 2.157897584, -0.170399539, 0.012501955

Update: see my Kahan cubic solver post

k = -B/(3A) = 2590/(3*1295) = 2/3
f(k)/A = -0.816567 = -0.934682³
f'(k)/A = -1.67619 = -1.29468² < 0
guess = k - 1.324718 (-1) max(0.934682, 1.29468) = 2.38175
Newton: 2.38175 → 2.19240 → 2.15892 → 2.15790 → x = 2.157897584

Deflate cubic to quadratic: A X² + E X + F = 0
IF |x³| > |D/A| THEN (F=-D/x, E=(F-C)/x) ELSE (E=Ax+B, F=Ex+C)

Above example, it is the THEN case.
1295 X² + 204.4773715 X − 2.758774116 = 0 ⇒ roots = 0.01250195572, -0.1703995399
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 Messages In This Thread Casio FX-115MS bug - Albert Chan - 10-31-2018 07:02 PM RE: Casio FX-115MS bug - klesl - 11-01-2018, 11:14 AM RE: Casio FX-115MS bug - ijabbott - 11-01-2018, 08:16 PM RE: Casio FX-115MS bug - G. Cook - 11-02-2018, 09:14 PM RE: Casio FX-115MS bug - Albert Chan - 11-03-2018, 02:41 PM RE: Casio FX-115MS bug - Albert Chan - 11-05-2018, 08:58 PM RE: Casio FX-115MS bug - Albert Chan - 11-07-2018, 08:15 PM RE: Casio FX-115MS bug - Albert Chan - 11-07-2018, 10:47 PM RE: Casio FX-115MS bug - Albert Chan - 11-08-2018, 04:17 PM RE: Casio FX-115MS bug - Albert Chan - 11-24-2018, 07:25 PM RE: Casio FX-115MS bug - ijabbott - 11-24-2018, 08:28 PM RE: Casio FX-115MS bug - klesl - 11-07-2018, 08:33 PM RE: Casio FX-115MS bug - Albert Chan - 11-08-2018, 02:51 PM RE: Casio FX-115MS bug - brickviking - 11-28-2018, 01:01 AM

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