function?output=Divide（fxmn）
if?nargin<4n=1e-6;end
if?nargin<3m=0;end
step=n;
t0=m;ft0=subs（f{x}{t0}）;
t1=t0+step;ft1=subs（f{x}{t1}）;
if?ft0>=ft1
????t2=t1+step;ft2=subs（f{x}{t2}）;
????while?ft1>ft2
????????t0=t1;
????????%ft0=ft1;
????????t1=t2;ft1=ft2;
????????step=2*step;t2=t1+step;ft2=subs（f{x}{t2}）;
????end
else?
????step=-step;
????t=t0;t0=t1;t1=t;ft=ft0;
????%ft0=ft1;
????ft1=ft;
????t2=t1+step;ft2=subs（f{x}{t2}）;
????while?ft1>ft2
????????t0=t1;
????????%ft0=ft1;
????????t1=t2;ft1=ft2;
????????step=2*step;t2=t1+step;ft2=subs（f{x}{t2}）;
????end
end
output=[t0t2];