Which of the following gives correct equation for Hooke's law for the spring? (F is force, k is spring constant and x is extension/compression in spring)

F=k-x

F=kx

F=k+x

Fs = -kx

Spring force: In an ideal spring, the force required to stretch a string from its equilibrium position is directly proportional to the extension of the spring.

This is known as Hooke's law and commonly written:

F_s = -kx

Where F_s is the spring force, x is the displacement from the equilibrium position and k is the spring constant.