Toán Lớp 8: Câu 1: tìm x biết:
(1-3x)^2 – 9.( x-3). (3+x) = 2.(x+3)
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Toán Lớp 8: Câu 1: tìm x biết:
(1-3x)^2 – 9.( x-3). (3+x) = 2.(x+3)
Comments ( 1 )
{\left( {1 – 3x} \right)^2} – 9\left( {x – 3} \right)\left( {3 + x} \right) = 2\left( {x + 3} \right)\\
\Leftrightarrow 1 – 6x + 9{x^2} – 9\left( {{x^2} – 9} \right) = 2x + 6\\
\Leftrightarrow 1 – 6x + 9{x^2} – 9{x^2} + 81 – 2x – 6 = 0\\
\Leftrightarrow – 8x + 76 = 0\\
\Leftrightarrow x = \dfrac{{76}}{8} = \dfrac{{19}}{2}\\
Vậy\,x = \dfrac{{19}}{2}
\end{array}$