format long
xl=0.5;
xu=2;
tolerance=0.0001;
rel_err=3;
fprintf('   xl       xu       xr    rel_error fxl.fxr change\n')
fprintf('-------- -------- -------- -------- -------- ------\n')
xr=(xl+xu)/2;
while (rel_err>tolerance)
%check whether xr in upper or lower interval
fxl=xl^3+4*xl^2-10;
fxr=xr^3+4*xr^2-10;
if (fxl*fxr<0)
	%root in lower interval
	%change upper bracket
	oldxu=xu;
       oldxl=xl;
       xu=xr;
       change="xu";
else
	%root in upper interval
	%change lower bracket
	oldxl=xl;
       oldxu=xu;
       xl=xr;
       change="xl";
end
fprintf('%8.6f %8.6f %8.6f %8.6f %4.2f %4s\n',oldxl,oldxu,xr,rel_err,(fxl*fxr),change)
oldxr=xr;
xr=(xl+xu)/2;
rel_err=abs((xr-oldxr)/xr)*100;
end
root=xr