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 !!