3D surface with axis guides

using Plots
pgfplotsx()

f(x, a) = begin
        1 / x + a * x ^ 2
    end
xs = collect(0.1:0.05:2.0)
as = collect(0.2:0.1:2.0)
x_grid = [x for x = xs for y = as]
a_grid = [y for x = xs for y = as]
plot(x_grid, a_grid, f.(x_grid, a_grid), st = :surface, xlabel = "longer xlabel", ylabel = "longer ylabel", zlabel = "longer zlabel")