(2a)^-2/a^2

Negative exponents are handled like this:  x^-1 = 1/x  so  x^-2 = 1/x²

This problem has (2a)^-2 which becomes 1/(2a)²  =  1/(4a²)

Therefore:  (2a)^-2 / a²  =  [ 1/(4a²) ] / a²  =  [ 1/(4a²) ] · [ 1/a² ]  =  1 / [ (4a²) · a² ]

   =  1 / ( 4a⁴ )