Obtain an expression for the fractional decrease in kinetic energy of a particle of mass 𝑚1 when it makes a head-on collision with a particle of mass 𝑚2 init

Obtain an expression for the fractional decrease in kinetic energy of a particle of mass 𝑚1 when it makes a head-on collision with a particle of mass 𝑚2 initially at rest and show that the transference of energy is maximum when the mass ratio is unity.