f(x) = -(2.0/x + 1.0*x**2) set xrange [0.001:3.25] set yrange [-10:0.1] set xlabel 'a' set ylabel 'E(a) (unite abritraire)' set style arrow 1 nohead lt 4 lc 'black' set object circle at first 1.0,f(1.0) radius char 0.5 \ fillcolor rgb 'black' fillstyle solid noborder set arrow from 0,f(1.0) to 1,f(1.0) arrowstyle 1 set arrow from 1.0,-10 to 1.0,f(1.0) arrowstyle 1 set label 'E(1) = K' at 0.25,f(1.0)+0.75 plot f(x) t 'Energie potentielle' lc 'black'