(12C Platinum) Cubic Equation

[Albert Chan]

(02-04-2019 08:13 PM)Thomas Klemm Wrote:  \(x^3 - 4x^2 + 6x - 24 = 0\)

Enter coefficients:

1 CF₀
-4 CF_j
6 CF_j
-24 CF_j

Enter guess:

20 R/S
4.0000

Above entered coefficients order are good for root finding, and to evaluate polynomial.

Example, with above entered polynomial, calculate f(X = 12.34)

1 Enter 12.34 [Δ%] [i] ; showed rate of 1134%, X = 1 + i

NPV 0 PMT FV CHS ; showed 1320.018504 <-- f(X)

Confirm with Horners rule:

12.34 Enter Enter Enter RCL 0
* RCL 1 +
* RCL 2 +
* RCL 3 + ; showed 1320.018504

Doing the same with reversed ordered entry is not as accurate:

24 CHS CF0
6 CFj
4 CHS CFj
1 CFj

1 Enter 12.34 [1/x] [Δ%] [i] ; showed rate of -91.89627229%, X = 1/(1 + i)

NPV ; showed 1320.018507, +3 ULP error