`b,` Theo Vi-ét: `x_1 + x_2 = 2m+1;x_1x_2 = m^2+5m`

Để tích các nghiệm bằng `6` thì:

`x_1 x_2 =6`

`<=>m^2+5m-6=0`

`<=>m^2-m+6m-6=0`

`<=>m(m-1)+6(m-1)=0`

`<=>(m-1)(m+6)=0`

`<=>`\(\left[ \begin{array}{l}m=1\\m=-6\end{array} \right.\) 

`TH1: m=1`

`=>x_1 +x_2 =3;x_1x_2 =6`

Ta có:

`x_1^2 +x_2^2 -1-(6+x_1x_2)`

`= (x_1 +x_2)^2-2x_1x_2 -1-(6+6)`

`= 3^2-2.6 -1-12`

`=-16`

`TH2: m=-6`

`=>x_1 +x_2 =-11;x_1x_2 =6`

Ta có:

`x_1^2 +x_2^2 -1-(6+x_1x_2)`

`= (x_1 +x_2)^2-2x_1x_2 -1-(6+6)`

`= (-11)^2-2.6 -1-12`

`=96`