If you're trying to say find f(x) = 5ˣ when x = -3
The answer would be [tex]\frac{1}{125}[/tex]
A negative exponent means to put that value in the reciprocal. So the reciprocal of 5 is [tex]\frac{1}{5}[/tex] . and the 3 means to multiply it 3 times like [tex](\frac{1}{5})(\frac{1}{5})(\frac{1}{5})[/tex] to get [tex]\frac{1}{125}[/tex]