\(\Delta'=4-\left(m+1\right)=3-m\ge0\Rightarrow m\le4\)
Theo hệ thức Viet: \(\left\{{}\begin{matrix}x_1+x_2=4\\x_1x_2=m+1\end{matrix}\right.\)
\(x_1^2+x_2^2-10x_1x_2=2020\)
\(\Leftrightarrow\left(x_1+x_2\right)^2-12x_1x_2=2020\)
\(\Leftrightarrow16-12\left(m+1\right)=2020\)
\(\Rightarrow m=-168\left(tm\right)\)