# User-defined linear function
f(x) = 2*x + 1

set terminal png size 400, 300
set output 'linear_function.png'

set title "Linear Function: f(x) = 2x + 1"
set xlabel "X-axis"
set ylabel "Y-axis"
set grid

# Plot the function
plot f(x) with lines title 'f(x) = 2x + 1'