---

    unset border
    set size square
    set xrange [-1.5:1.5]
    set yrange [-1.5:1.5]
    plot x*x*x             lw 2 , x*x+x-1 lw 2 lt 3
    plot x*x*x-x           lw 2 , x*x-1   lw 2 lt 3
    set yrange [-2.5:0.5]
    plot x*x*x-x*x         lw 2 , x-1     lw 2 lt 3
    set yrange [-1.5:1.5]
    plot x*x*x-x*x-x+1     lw 2 , 0       lw 2 lt 3