In simple harmonic motion, a particle is oscillating in such a way that its total energy remains conserved. When this particle reaches its two extreme positions, its potential energy at the extreme positions become:

Explanation

In SHM, kinetic energy is maximum at mean position and zero at the extreme positions while potential energy is zero at mean position and maximum at the extreme positions. In SHM when a particle reach its extreme position so at that point its velocity become zero and all the energy it has is just potential energy because if we drop the particle from extreme position so it come back to its originsl position without any externsl force by using its stored potential energy and these extreme positions are the positions where the particle have maximum potential energy. Result: So at extreme postions potential enegy is maximum and at starting point it is minimum.