a/ \(\Delta'=m^2-5m^2+16=16-4m^2\ge0\Rightarrow-2\le m\le2\)
b/ Theo định lý Viet: \(\left\{{}\begin{matrix}x_1+x_2=2m\\x_1x_2=5m^2-16\end{matrix}\right.\)
\(A=5x_1^2+3x_1x_2-17x_1+5x_2^2+3x_1x_2-17x_2\)
\(\Rightarrow A=5\left(\left(x_1+x_2\right)^2-2x_1x_2\right)+6x_1x_2-17\left(x_1+x_2\right)\)
\(\Rightarrow A=5\left(x_1+x_2\right)^2-4x_1x_2-17\left(x_1+x_2\right)\)
\(\Rightarrow A=5\left(2m\right)^2-4\left(5m^2-16\right)-17.2m=64-34m\)
Mà \(-2\le m\le2\) \(\Rightarrow-4\le A\le132\)
\(\Rightarrow\left\{{}\begin{matrix}A_{max}=132\\A_{min}=-4\end{matrix}\right.\)