Positive indices

a)(xy)^-2

= 1/(xy)^2

b) 5a^-3

= 5/ a^3

c) 3x^2y^3z^-1

= 3x^2y^3/ z

d) b^-4 c^3

= c^3/ b^4

e) (pqrs)^0

= 1 (Anything raised to 0 is 1)

To simplify the expression (xy)^-2, we can apply the rule of positive indices:

(xy)^-2 = 1/(xy)^2

Now, let's simplify the denominator by expanding (xy)^2:

(xy)^2 = (x^2)(y^2)

Finally, substituting this back into our expression, we have:

1/(xy)^2 = 1/(x^2)(y^2)

Therefore, the simplified form of (xy)^-2 is 1/(x^2)(y^2).