Giải thích các bước giải:
Ta có:
\(\begin{array}{l}
1,\\
3{x^2} + 5,2 = 32,2\\
\Leftrightarrow 3{x^2} = 32,2 - 5,2\\
\Leftrightarrow 3{x^2} = 27\\
\Leftrightarrow {x^2} = 27:3\\
\Leftrightarrow {x^2} = 9\\
\Leftrightarrow {x^2} = {3^2}\\
\Leftrightarrow \left[ \begin{array}{l}
x = 3\\
x = - 3
\end{array} \right.\\
2,\\
129 - 50{x^2} = - 159\\
\Leftrightarrow 50{x^2} = 129 - \left( { - 159} \right)\\
\Leftrightarrow 50{x^2} = 288\\
\Leftrightarrow {x^2} = 288:50\\
\Leftrightarrow {x^2} = \dfrac{{144}}{{25}}\\
\Leftrightarrow {x^2} = {\left( {\dfrac{{12}}{5}} \right)^2}\\
\Leftrightarrow \left[ \begin{array}{l}
x = \dfrac{{12}}{5}\\
x = - \dfrac{{12}}{5}
\end{array} \right.\\
3,\\
3,2 - 5\sqrt x = \dfrac{1}{5}\\
\Leftrightarrow 5\sqrt x = 3,2 - \dfrac{1}{5}\\
\Leftrightarrow 5\sqrt x = 3\\
\Leftrightarrow \sqrt x = \dfrac{3}{5}\\
\Leftrightarrow x = {\left( {\dfrac{3}{5}} \right)^2}\\
\Leftrightarrow x = \dfrac{9}{{25}}
\end{array}\)
