Toán Lớp 10: giải ptr: 21 + √x ² – 6x + 9 =4 x
giúp mik với :))
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Toán Lớp 10: giải ptr: 21 + √x ² – 6x + 9 =4 x
giúp mik với :))
Comments ( 1 )
21 + \sqrt {{x^2} – 6x + 9} = 4x\\
\Leftrightarrow \sqrt {{{\left( {x – 3} \right)}^2}} = 4x – 21\left( {dk:x \ge \dfrac{{21}}{4}} \right)\\
\Leftrightarrow \left| {x – 3} \right| = 4x – 21\\
\Leftrightarrow \left[ \begin{array}{l}
x – 3 = 4x – 21\\
x – 3 = 21 – 4x
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
3x = 18\\
5x = 24
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
x = 6\left( {tm} \right)\\
x = \dfrac{{24}}{5}\left( {ktm} \right)
\end{array} \right.\\
Vậy\,x = 6
\end{array}$