Simplify the following expression. Assume $\displaystyle {x}>{0}$.
$\displaystyle {\left({16}{x}\right)}^{{{1}/{2}}}\cdot{\left(-{2}{x}^{{-{2}/{3}}}\right)}$

A) The answer can be written in the form $\displaystyle {C}{x}^{{a}}$ where
the coefficient $\displaystyle {C}$ is: Preview Question 6 Part 1 of 2  
and the exponent $\displaystyle {a}$ is: Preview Question 6 Part 2 of 2   Note: enter the exponent as a reduced fraction or integer.