reset
set border
# set xtics 1
# set ytics 20
# set xzeroaxis lt 9 lw 2
# set yzeroaxis lt 9 lw 2
set style line 1 lt -1 lw 2
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 [-20:20]
# set samples 1000
set key off
f(x)=0.25*x**2-15
g(x)=0.25*x**2-15
h(x)=-4+sqrt(x+16)
plot f(x) ls 1
# plot f(x) ls 1,g(x) ls 2, h(x) ls 3