Simplify?

25 1/2 as in 25^(1/2) --> sqrt(25) = 5.

(sqrt9xy^2)^4 --> (sqrt9xy^2)(sqrt9xy^2)(sqrt9xy^2)(sqrt9xy^2)

(sqrt9xy^2)(sqrt9xy^2) = 9x^2y^4

Now, we can just square this term [9x^2y^4] since we have another (sqrt9xy^2)(sqrt9xy^2) -->

(9x^2y^4)(9x^2y^4) = 81x^4y^8.

An easier way is to just distribute the ^4 to each of the terms -->

(sqrt9xy^2)^4 = (sqrt9)^4*x^4*(y^2)^4 = 81x^4y^8.

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EDITED: First answer.

I don't know what the first question means but the second has  been well answered.

Thanks Aziz