Question

Which expression is equivalent to -(5y)^-4 ?

Answer 1

The first step for solving this expression is to express it with a positive exponent using $a^{-n} = \frac{1}{ a^{n} }$.
$- \frac{1}{(5y)^{4} }$
According to the exponent rules,, to raise a product to a power you must raise each factor to that power. This rule will change the expression to the following:
$-\frac{1}{625 y^{4} }$
This makes the correct answer to your question $-\frac{1}{625 y^{4} }$,, or option D.
Let me know if you have any further questions.
:)