Đáp án:
\(A=\dfrac{1}{y}\)
Cách giải chi tiết:
$\begin{array}{l}
A = \frac{y}{x}.\sqrt {\frac{{{x^2}}}{{{y^4}}}} = \frac{y}{x}.\sqrt {{{\left( {\frac{x}{{{y^2}}}} \right)}^2}} = \frac{y}{x}.\left| {\frac{x}{{{y^2}}}} \right| = \frac{y}{x}.\frac{{\left| x \right|}}{{{y^2}}}\\
= \frac{{\left| x \right|}}{{xy}} = \frac{x}{{xy}}\,\,\,\,\left( {do\,\,\,\,x > 0 \Rightarrow \left| x \right| = x} \right)\\
= \frac{1}{y}.
\end{array}$
