Hi all,
I figured with Dave's fondness of casios here, I'd be able to find an answer.
I have a bunch of old casio calculators (thanks Dave...
) My most recent addition is a Fx-5000F. I absolutely love it, so much more useful than newer calculators, and in a much smaller package. I especially love using the scientific formulae. That's what this question is about. I use the quadratic formula often, so I very often use the first formula on the calculator. Sure, I could solve it by hand, but using the formula on the calculator is much quicker. That's the point.
Anyway, I'm trying to solve a quadratic with A=1, B=0.15, C=-7.7E-13. Now, I realize C is quite small, but I've done many other calculations on the calculator which turned out accurate, even at those orders of magnitude.
When put into the first formula (Press 1, then FMLA), it gives roots of -0.15 (correct) and 4.5E-13(wrong). The actual other root is 5.1E-13. Any ideas?
Please don't berate me for using a calculator to do this. This is more of a question of WHY it's wrong, not that it IS wrong. It's easy to calculate this other ways obviously.
EDIT: I realize that it probably has something to do with the rounding in the calculator, but I'm not about to dig through the entire 200 page manual to find the specs on it.
In fact, if I change C to = -7.7E-12, the formula actually gives the correct answer. Gahh, maybe I will dig through the manual. I've read it once, I don't remember anything about accuracy in formulae though.