reset
set border
set xtics 1
set ytics 5
set xzeroaxis lt 9 lw 4
set yzeroaxis lt 9 lw 4
set style line 1 lt -1 lw 4
set style line 2 lt -1 lw 1
set style line 3 lt 12 lw 3
set grid ls 2
show grid
set xrange [-10:10]
set yrange [-50:10]
# set samples 1000
set key off
f(x)=x**2+x-42
# g(x)=x**2+x-42
# h(x)=-4+sqrt(x+16)
plot f(x) ls 1
# plot f(x) ls 1,g(x) ls 2, h(x) ls 3