Toán Lớp 8: Tìm x : x² – (x+1)(x² – x + 1) = x
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Toán Lớp 8: Tìm x : x² – (x+1)(x² – x + 1) = x
Comments ( 2 )
{x^2} – \left( {x + 1} \right)\left( {{x^2} – x + 1} \right) = x\\
\Leftrightarrow {x^2} – \left( {{x^3} + 1} \right) = x\\
\Leftrightarrow {x^2} – {x^3} – 1 = x\\
\Rightarrow SAI\,\,DE\\
\Rightarrow \,\,SUA\,\,DE:\\
{x^3} – \left( {x + 1} \right)\left( {{x^2} – x + 1} \right) = x\\
\Leftrightarrow {x^3} – \left( {{x^3} + 1} \right) = x\\
\Leftrightarrow {x^3} – {x^3} – 1 = x\\
\Leftrightarrow – 1 = x\\
\Rightarrow x = – 1
\end{array}\]