x=linspace(-3.1,2.4,100);
y=matlab_03b_fce(x);
r1=fzero('matlab_03b_fce',-3);
r2=fzero('matlab_03b_fce',0);
r3=fzero('matlab_03b_fce',2);
plot(x,y,r1,matlab_03b_fce(r1),'x',r2,matlab_03b_fce(r2),'x',r3,matlab_03b_fce(r3),'x');