Regula Falsi

program regula_falsi;
uses crt;
label ulang;
var
x1,x2,x3,y1,y2,y3 : real;
i : integer;
Ab :char;
data1 : real;
begin

ulang:
clrscr;
writeln('Tentukan nilai akar dari persamaan f(x)=x^3+x^2-3x-3=0 dengan Regula Falsi');
write('Masukan nilai x1 = ');readln(x1);
y1 := x1 * x1 * x1 + x1 * x1 - 3 * x1 - 3;
writeln(' Nilai f(x1)= ',y1:0:4);
repeat
begin
write( 'Masukan nilai x2 = ' ); readln(x2);
y2 := x2 * x2 * x2 + x2 * x2 - 3 * x2 - 3;
write(' Nilai f(x2)= ',y2:0:4);
end;
if (y1*y2)<0 then
Writeln(' Syarat Nilai Ok')
else
Writeln(' Nilai X2 Belum Sesuai');
until ( y1 * y2 ) <0;
writeln;
writeln('Penyelesaian persamaan karekteristik dengan metoda regula falsi');
writeln('----------------------------------------------------------------------');
writeln(' n x f(x) error ');
writeln('----------------------------------------------------------------------');
repeat
begin
i:= i + 1; x3 := ( x2-( y2 / ( y2 - y1))*(x2-x1));
y3 := x3 * x3 * x3 + x3 * x3 - 3 * x3 - 3;
if i<10 then
writeln(' ',i,' : ',x3,' : ',y3,' : ',abs(y3),' : ')
else
writeln(i,' : ',x3,' : ',y3,' : ',abs(y3),' : ');
if ( y1 * y3 ) <0 then
begin
x2 := x3 ; y2 := y3 ;
end
else
begin
x1 := x3 ; y1 := y3;
end;
end;
until abs( y3 ) < 1E-08;
writeln('----------------------------------------------------------------------');
writeln('Akar persamaannya= ',x3);
writeln('Errornya=' ,abs( y3 ));
writeln('----------------------------------------------------------------------');
writeln('Apakah anda ingin mengulangi (y/t): ');
readln(ab);
if (ab='y') or (ab='Y') then
goto ulang;
end.