Since Mechanical Energy is defined as Sum of Kinetic Energy and Potential Energy , It should be conserved at all points.

Let us consider a freely falling body ,It is at a height ‘H’ from the ground .

Let the Total Mechanical Energy be M.E joules

Considering its motion at three points A,B & C .

At A velocity v = 0 hence its Kinetic Energy is zero ,but its Potential energy = mgh

hence ,Mechanical Energy = Kinetic Energy + Potential Energy

M.E = mgh -- (i)

At B velocity v = v1 ,Kinetic Energy will be and Potential Energy will be mgh/2

hence, Mechanical Energy = Kinetic Energy + Potential Energy

M.E = + mg --(ii)

At C velocity v = v2 ,Kinetic Energy will be and potential Energy will be Zero

hence, Mechanical Energy = Kinetic Energy + Potential Energy

M.E = +0 -- (iii)

Since Mechanical Energy is Conserved , We can say that M.E at points A,B & C or Equations (i) ,(ii) & (iii) will be equal.