The correct option is B 5
Given: (xy)z=(yx)−5
To Find: Value of z
(xy)z=(yx)−5
Applying the exponent rule (ab)−n=(ba)n on R.H.S of the equation to remove the negative sign from the exponent.
⇒(xy)z=(xy)5
Here, as bases are same, the exponents on both the sides must also be the same for the equality.
⇒z=5
Therefore, option (b.) is the correct one.