Which could be the first step in simplifying this expression? check all that apply. (x^3x^-6)^2

If the expression is what I understand it is, this is my answer. (x to the third times x to the negative sixth all squared)

First, i would simplify what is inside the parentheses. x^-6 is the equivalent to
1/x^6. Therefore, the expression inside the parentheses is a fraction: x^3/x^6.

When dividing numbers with exponents, just subtract the exponents. 
3-6= -3     so the simplification of the expression in the parentheses is 1/x^3.

To finish the problem, I would apply the square from outside the parentheses to the values inside them. In this way, the exponent would be multiplied by 2.

Our final answer is 1/x^6.