Horizontal Spring Pulled from Equilibrium?

[riseofphoenix]

I don't necessarily understand the explanation given to the solution.
Is it basically saying:

A (valley) --> 0 (equilibrium) --> -A (valley) --> 0 (equilibrium) --> A (valley)?

 

[SammyS]

I don't necessarily understand the explanation given to the solution.
Is it basically saying:

A (valley) --> 0 (equilibrium) --> -A (valley) --> 0 (equilibrium) --> A (valley)?

What valley are you referring to?

The block moves horizontally.