Two springs supporting a mass verticle

[PsychonautQQ]

Homework Statement

Two springs have spring constants k1 and k2, are in a vertical position to support a single object of mass m. Show that the angular frequency of oscillation is ((k1+k2)/m)^(1/2) if the springs are in parallel.

The Attempt at a Solution

The book then goes on to explain
F = ma = -k1*x - k2*x
a + ((k1+k2)*x) / m = 0
where (k1+k2)/m = w^2
my question is why is gravity neglected?

 

[Doc Al]

They aren't really neglecting gravity. Note that the displacement (the x) is measured from the equilibrium position, so the effect of gravity is already included. (Gravity, being a constant force, merely shifts the zero point.)