Toán Lớp 9: tìm m để x^2+2(m+1)x-5m+9=0 có 2 nghiệm phân biệt
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Toán Lớp 9: tìm m để x^2+2(m+1)x-5m+9=0 có 2 nghiệm phân biệt
Comments ( 2 )
m > 1\\
m < – 8
\end{array} \right.\)
\to \Delta ‘ > 0\\
\to {m^2} + 2m + 1 + 5m – 9 > 0\\
\to {m^2} + 7m – 8 > 0\\
\to \left( {m + 8} \right)\left( {m – 1} \right) > 0\\
\to \left[ \begin{array}{l}
\left\{ \begin{array}{l}
m + 8 > 0\\
m – 1 > 0
\end{array} \right.\\
\left\{ \begin{array}{l}
m + 8 < 0\\
m – 1 < 0
\end{array} \right.
\end{array} \right.\\
\to \left[ \begin{array}{l}
m > 1\\
m < – 8
\end{array} \right.
\end{array}\)