reset
set border
set xtics 1
set ytics 2
set grid
set xzeroaxis lt 2 lw 2
set yzeroaxis lt 2 lw 2
set style line 1 lt 0 lw 0
set style line 2 lt 5 lw 3
set style line 3 lt 12 lw 3
set xrange [-5:5]
set yrange [-20:20]
f(x)=-3*x+1
g(x)=-x**2+16
h(x)=f(x)/g(x)
k(x)=-x**2-3*x+18
m(x)=0*x
set key off
plot m(x) lt 2