DO
    CLS : INPUT "Estremi dell'intervallo"; A, B
LOOP UNTIL (A >= 0 AND B >= 0) AND B > A
SCREEN 12
COLOR 14: LINE (0, 240)-(640, 240)
LOCATE 29, 54: PRINT "by Peter '94 and Lauretta";
COLOR 11: Incr = 25
DIM E(639), Ord(639)
FOR I = 0 TO 639
    E(I) = I
    X = A + E(I) * (B - A) / 640
    IF X = 0 THEN COLOR 14: LINE (I, 0)-(I, 480): COLOR 11
    IF X ^ 4 - 2 * X + 1 <> 0 THEN Ord(I) = (SQR(X) + 1) / (X ^ 4 - 2 * X + 1)
    IF ABS(X ^ 4 - 2 * X + 1) < .0001 THEN
        Incr = Incr + 1
        COLOR 14: LOCATE Incr, 79 - LEN(STR$(X)): PRINT STR$(X): COLOR 11
    END IF
    IF ABS(Ord(I)) > 1000 THEN Ord(I) = SGN(Ord(I)) * 1000
    IF I > 0 THEN LINE (E(I), 240 - 10 * Ord(I))-(E(I - 1), 240 - 10 * Ord(I - 1))
NEXT
DO WHILE A$ = ""
    A$ = INKEY$
LOOP