reset set border set xtics 5 set ytics 10 set xzeroaxis lt 9 lw 4 set yzeroaxis lt 9 lw 4 set style line 1 lt 1 lw 3 set style line 2 lt 3 lw 3 set style line 3 lt 10 lw 3 set style line 4 lt 12 lw 3 set style line 5 lt 9 lw 1 set grid ls 5 show grid set xrange [-30:10] set yrange [-50:100] # set samples 1000 set key on f(x)=x**2+52*x+667 g(x)=-(x**2)+6*x+24.0625 h(x)=x**2+5*x+61 i(x)=4*x**2+40*x+84 # plot f(x) ls 1 plot f(x) ls 1,g(x) ls 2, h(x) ls 3, i(x) ls 4