How can you prove 4=5.. Intersting and logical reply

Let us assume    -20 = -20

So    16-36 = 25-45

So    16-4*9 = 25-5*9

So    16-2*4*9/2 = 25-2*5*9/2

by adding 9/2 whole square both sides....

So    16-2*4*9/2+(9/2)² = 25-2*5*9/2+(9/2)²

But   {16-2*4*9/2+(9/2)²} is complete squaure of (4-9/2).

and {25-2*5*9/2+(9/2)²} is complete squaure of (5-9/2).

Therefor the equation is  (4-92)² = (5-9/2)²

By eliminating Square we will get (4-9/2) = (5-9/2)

Now by eliminating 9/2 from both sides we get  4  = 5 !!