Hãy tính: \(5xy\sqrt {\frac{{25{x^2}}}{{{y^6}}}} \left( {x 0} \right)\).

* Hướng dẫn giải

 \(\begin{array}{l} 5xy\sqrt {\frac{{25{x^2}}}{{{y^6}}}} \left( {x < 0,y > 0} \right)\\ = 5xy\frac{{\sqrt {25{x^2}} }}{{\sqrt {{y^6}} }} = 5xy\frac{{\sqrt {{{\left( {5x} \right)}^2}} }}{{\sqrt {{{\left( {{y^3}} \right)}^2}} }}\\ = 5xy\frac{{\left| {5x} \right|}}{{\left| {{y^3}} \right|}} = 5xy\frac{{ - 5x}}{{{y^3}}} = \frac{{ - 25{x^2}}}{y} \end{array}\)