\(41:x^2-\left(m-1\right)x+m+2=0\)
\(\Leftrightarrow\Delta=\left(m-1\right)^2-4\left(m+2\right)=m^2-6m-7>0\Leftrightarrow\left[{}\begin{matrix}m< -1\\m>7\end{matrix}\right.\)
\(x1;x2\ne0\Rightarrow m\ne-2\)
\(\dfrac{1}{x1^{^2}}+\dfrac{1}{x2^2}>1\)\(\Leftrightarrow\dfrac{\left(x1+x2\right)^2-2x1x2}{\left(x1.x2\right)^2}>1\Leftrightarrow\left(x1+x2\right)^2-2x1x2-\left(x1x2\right)^2>0\Leftrightarrow\left(m-1\right)^2-2\left(m+2\right)-\left(m+2\right)^2>0\Leftrightarrow m< -\dfrac{7}{8}\)
\(\Rightarrow m\in(-\infty;-1)/\left\{-2\right\}\Rightarrow B\)
\(42::17x^2-92xy+90y ^2-9=0\)
(hình như đề sai )
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