Which expression is equivalent to (5^-2) (5^-1)

The rule for multiplying similar bases with exponents:

(a^b) (a^c) = a^ (b+c)

In this case we have:

(5^-2) (5^-1)

5^ (-2-1)

5^ (-3)

The rule for negative exponents:

a^ (-b) = 1 / (a^b)

So in this case:

5^ (-3) is equal to

1 / (5^3)

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