The rule about negative exponents is that you put the base under "1" in a fraction and the negative exponent becomes positive. For example, [tex] x^{-1} [/tex] becomes [tex] \frac{1}{x} [/tex]. So in your case, [tex] \frac{1}{4} ^{-2} = \frac{1}{ \frac{1}{4} ^{2} } = \frac{1}{ \frac{1}{16} } =16[/tex]
