Giải thích các bước giải:
$\begin{array}{l}
a)\sqrt {{x^4}} = \sqrt {{{\left( {{x^2}} \right)}^2}} = {x^2}\\
b)\sqrt {{y^6}} = \sqrt {{{\left( {{y^3}} \right)}^2}} = \left| {{y^3}} \right|\\
c)\sqrt {64{m^8}} = \sqrt {{{\left( {8{m^4}} \right)}^2}} = 8{m^4}\\
h)\sqrt {{{\left( {x + 1} \right)}^2}} = \left| {x + 1} \right|\\
i)\sqrt {{{\left( {2x - 3} \right)}^2}} = \left| {2x - 3} \right|\\
j)\sqrt {{{\left( {3 - x} \right)}^4}} = \sqrt {{{\left( {{{\left( {3 - x} \right)}^2}} \right)}^2}} = {\left( {3 - x} \right)^2}\\
k)\sqrt {{{\left( {4 - 3x} \right)}^6}} = \sqrt {{{\left( {{{\left( {4 - 3x} \right)}^3}} \right)}^2}} = \left| {{{\left( {4 - 3x} \right)}^3}} \right|\\
l)\sqrt {4{x^2} + 4x + 1} = \sqrt {{{\left( {2x + 1} \right)}^2}} = \left| {2x + 1} \right|\\
m)\sqrt {{x^2} - x + \dfrac{1}{4}} = \sqrt {{{\left( {x - \dfrac{1}{2}} \right)}^2}} = \left| {x - \dfrac{1}{2}} \right|\\
n)\sqrt {1 - 6x + 9{x^2}} = \sqrt {{{\left( {1 - 3x} \right)}^2}} = \left| {1 - 3x} \right|\\
o)x - \sqrt {1 - 2x + {x^2}} = x - \sqrt {{{\left( {1 - x} \right)}^2}} = x - \left| {x - 1} \right|\\
p)\sqrt {{x^2} - 10x + 25} - 2 = \sqrt {{{\left( {x - 5} \right)}^2}} - 2 = \left| {x - 5} \right| - 2\\
q)\sqrt {x - 6\sqrt {x - 9} } = \sqrt {x - 9 - 6\sqrt {x - 9} + 9} = \sqrt {{{\left( {\sqrt {x - 9} - 3} \right)}^2}} = \left| {\sqrt {x - 9} - 3} \right|\\
r)x\ne 2\to \dfrac{{\sqrt {{x^2} - 4x + 4} }}{{2 - x}} = \dfrac{{\sqrt {{{\left( {x - 2} \right)}^2}} }}{{2 - x}} = \dfrac{{\left| {x - 2} \right|}}{{2 - x}}
\end{array}$
