Toán Lớp 8: Dạng tìm x
x(x+3)-2(x+6)=0
4(x-1)-x(x-1)=0
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Toán Lớp 8: Dạng tìm x
x(x+3)-2(x+6)=0
4(x-1)-x(x-1)=0
Comments ( 1 )
a)\\
x\left( {x + 3} \right) – 2.\left( {x + 6} \right) = 0\\
\Leftrightarrow {x^2} + 3x – 2x – 12 = 0\\
\Leftrightarrow {x^2} + x – 12 = 0\\
\Leftrightarrow {x^2} + 4x – 3x – 12 = 0\\
\Leftrightarrow \left( {x + 4} \right)\left( {x – 3} \right) = 0\\
\Leftrightarrow \left[ \begin{array}{l}
x + 4 = 0\\
x – 3 = 0
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
x = – 4\\
x = 3
\end{array} \right.\\
Vậy\,x = – 4;x = 3\\
b)\\
4.\left( {x – 1} \right) – x\left( {x – 1} \right) = 0\\
\Leftrightarrow \left( {x – 1} \right).\left( {4 – x} \right) = 0\\
\Leftrightarrow \left[ \begin{array}{l}
x – 1 = 0\\
4 – x = 0
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
x = 1\\
x = 4
\end{array} \right.\\
Vậy\,x = 1;x = 4
\end{array}$