\(f\left(x\right)=x^2-2mx+m^2-3m+2\)

\(\Leftrightarrow f\left(x\right)=\left(x-m\right)^2-3m+2\)

Ta có : \(\left(x-m\right)^2\ge0\)

Để \(f\left(x\right)>0\)

\(\Leftrightarrow-3m+2>0\)

\(\Leftrightarrow m>-\frac{2}{3}\)

Vậy để \(f\left(x\right)>0\forall x\inℝ\Leftrightarrow m>-\frac{2}{3}\)

P/s : K biết có sai chỗ nào k ạ ? Check hộ e :)

Bài vừa rồi mik làm sai nhé :(( Làm lại :

\(f\left(x\right)=x^2-2mx+m^2-3m+2\)

\(\Leftrightarrow f\left(x\right)=\left(x-m\right)^2-3m+2\)

Ta thấy : \(\left(x-m\right)^2\ge0\)

Để \(f\left(x\right)>0\)

\(\Leftrightarrow-3m+2>0\)

\(\Leftrightarrow2>3m\)

\(\Leftrightarrow m< \frac{2}{3}\)

Vậy để \(f\left(x\right)>0\forall x\inℝ\Leftrightarrow m< \frac{2}{3}\)

Để tam thức ko đổi dấu trên R

\(\Leftrightarrow\left\{{}\begin{matrix}m-1>0\\\Delta'=m^2-\left(m-1\right)\left(3m-2\right)< 0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}m>1\\-2m^2+5m-2< 0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}m>1\\\left[{}\begin{matrix}m< \frac{1}{2}\\m>2\end{matrix}\right.\end{matrix}\right.\) \(\Rightarrow m>2\)

\(\Delta'=m^2-2m+3>0\) ; \(\forall x\)

Do đó bài toán thỏa mãn khi pt \(f\left(x\right)=0\) có 2 nghiệm thỏa mãn: \(x_1< -1< 2< x_2\)

\(\Leftrightarrow\left\{{}\begin{matrix}a.f\left(-1\right)< 0\\a.f\left(2\right)< 0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}1.\left(1-2m+2m-3\right)< 0\\1\left(4+4m+2m-3\right)< 0\end{matrix}\right.\)

\(\Leftrightarrow6m+1< 0\Rightarrow m< -\dfrac{1}{6}\)

\(f\left(x\right)=m\left(m+2\right)x^2+2mx+2>0\)

\(\Leftrightarrow\left\{{}\begin{matrix}a>0\\\Delta'< 0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}m\left(m+2\right)>0\\m^2-2m^2-4m< 0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}\left[{}\begin{matrix}x< -2\\x>0\end{matrix}\right.\\\left[{}\begin{matrix}x< -4\\x>0\end{matrix}\right.\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x< -2\\x>0\end{matrix}\right.\)

Để tam thức ko đổi dấu trên R

\(\Leftrightarrow\left\{{}\begin{matrix}m\left(m+2\right)>0\\\Delta'=m^2-2m\left(m+2\right)< 0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}m\left(m+2\right)>0\\-m^2-4m< 0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}\left[{}\begin{matrix}m>0\\m< -2\end{matrix}\right.\\\left[{}\begin{matrix}m>0\\m< -4\end{matrix}\right.\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}m>0\\m< -4\end{matrix}\right.\)

1.

\(2\left|x-m\right|+x^2+2>2mx\)

\(\Leftrightarrow\left(x-m\right)^2+2\left|x-m\right|-m^2+2>0\)

\(\Leftrightarrow t^2+2t-m^2+2>0\left(t=\left|x-m\right|\ge0\right)\)

\(\Leftrightarrow m^2< f\left(t\right)=t^2+2t+2\)

Yêu cầu bài toán thỏa mãn khi \(m^2< minf\left(t\right)=2\)

\(\Leftrightarrow-\sqrt{2}< m< 2\)

Vậy \(-\sqrt{2}< m< 2\)

2.

\(x^2+2\left|x+m\right|+2mx+3m^2-3m+1< 0\)

\(\Leftrightarrow\left(x+m\right)^2+2\left|x+m\right|+2m^2-3m+1< 0\)

\(\Leftrightarrow\left(\left|x+m\right|+1\right)^2< -2m^2+3m\)

Ta có \(VT=\left(\left|x+m\right|+1\right)^2=\left(-\left|x+m\right|-1\right)^2\le\left(-1\right)^2=1\)

Yêu cầu bài toán thỏa mãn khi \(VP=-2m^2+3m>1\)

\(\Leftrightarrow2m^2-3m+1< 0\)

\(\Leftrightarrow\dfrac{1}{2}< m< 1\)

Ta có \(f\left(x\right)>0,\forall x\in\left(0;1\right)\)

\(\Leftrightarrow-x^2-2\left(m-1\right)x+2m-1>0,\forall x\left(0;1\right)\)

\(\Leftrightarrow-2m\left(x-1\right)>x^2-2x+1,\forall x\in\left(0;1\right)\) (*)

Vì \(x\in\left(0;1\right)\Rightarrow x-1< 0\) nên (*) \(\Leftrightarrow-2m< \dfrac{x^2-2x+1}{x-1}=x-1=g\left(x\right),\forall x\in\left(0;1\right)\)

\(\Leftrightarrow-2m\le g\left(0\right)=-1\Leftrightarrow m\ge\dfrac{1}{2}\)