420 "X" CLEAR : CLS : INPUT "Max:1/Min:-1:";G,"Interv:";A#,B#:H=1000:D=1E-6:I=1: CLS 
  421 K#=(A#+B#-D)/2:L#=K#+D:X#=K#: GOSUB 1:J#=F#*G:X#=L#: GOSUB 1:M#=F#*G: IF J#<M# THEN 424
  422 IF J#=M# THEN 427
  423 B#=L#: GOTO 425
  424 A#=K#
  425 IF I>H THEN 429
  426 I=I+1: IF B#-A#>2*D THEN 421
  427 C#=(K#+L#)/2: ON G+2 GOTO 430,428,428
  428 PRINT "x-max=";C#:X#=C#: GOSUB 1: PRINT "f(x)=";F#*G: END 
  429 PRINT "too slow": END 
  430 PRINT "x-min=";C#:X#=C#: GOSUB 1: PRINT "f(x)=";F#: END