pemdas, so exponent before multiply
so do a^-1/2 then multiply it by 2
remember that [tex]x^ \frac{m}{n}= \sqrt[n]{x^m} [/tex] and
[tex]x^{-m}= \frac{1}{x^m} [/tex]
therefor, [tex]a^ \frac{-1}{2}= \frac{1}{a^ \frac{1}{2} } = \frac{1}{ \sqrt{a} } [/tex]
the we multiply by 2
[tex] \frac{2}{ \sqrt{a} } [/tex]
