(71B) Polynomial Coefficients from a given list of roots -- for the HP-71B
06-13-2021, 03:28 PM (This post was last modified: 06-13-2021 03:58 PM by C.Ret.)
Post: #2
 C.Ret Member Posts: 249 Joined: Dec 2013
RE: Polynomial Coefficients from a given list of roots -- for the HP-71B
HI,

Here is the same task without DATA/READ structure, only one FOR TO NEXT loop and a more convivial interface for output and input :

10 DESTROY A,D,I,R @ OPTION BASE 0 @ DIM A(29) @ A(0)=1
12 INPUT "Add root x.=";R @ D=D+1
14 FOR I= D TO 0 STEP -1 @ IF I>0 THEN A(I)=A(I-1)-R*A(I) ELSE A(0)=-R*A(0)
16 GOSUB 20 @ NEXT I @ PAUSE @ GOTO 12

20 IF A(I)>0 AND I<D THEN DISP "+"; ELSE IF A(I)<0 THEN DISP "-";
22 IF A(I)=0 THEN RETURN ELSE IF ABS(A(I))#1 OR I=0 THEN DISP STR$(ABS(A(I)); 24 IF I<1 THEN RETURN ELSE DISP "x"; @ IF I>1 THEN DISP "^"&STR$(I);
26 RETURN

Usage :
New polynomials coefficients are deduce at each step by multiplying the previous polynomial by (x-r). This increase its degree by one unit (variable D indicate polynomial's degree)
1. Start the program with [RUN] or any appropriate method.
2. When prompt, enter value of the root to add and press [END LINE]
3. The actual polynomial is displayed.
4. To continue adding a root from step #2, press [f][CONT]
5. To clear the actual polynomial and restart with a new set of roots, press [RUN]

Example 1:
Code:
>                                 (RUN) Add root x.=                     1 (ENDLINE) x-1                               (f)(CONT) Add root x.=                     2 (ENDLINE) x^2-3x+2                          (f)(CONT) Add root x.=                     3 (END LINE) x^3-6x^2+11x-6
Example 2:
Code:
x^3-6x^2+11x-6                    (RUN) Add root x.=                     -1-SQRT(3) (ENDLINE) x+2.73205080757                   (f)(CONT) Add root x.=                     -1+SQRT(3) (ENDLINE) x^2+2x-2                          (ON) >_
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 Messages In This Thread (71B) Polynomial Coefficients from a given list of roots -- for the HP-71B - Namir - 12-26-2018, 12:11 AM RE: Polynomial Coefficients from a given list of roots -- for the HP-71B - C.Ret - 06-13-2021 03:28 PM

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