\[2x^{2} - (b + 2)x + b + 4 = 0\]
\[D = (b + 2)^{2} - 4 \cdot 2 \cdot (b + 4) =\]
\[= b^{2} + 4b - 8b - 32 =\]
\[= b^{2} - 4b - 28 > 0\]
\[b^{2} - 4b + 28 = 0\]
\[D = 4 + 28 = 32\]
\[b_{1,2} = 2 \pm 4\sqrt{2}.\]
\[x_{1} + x_{2} = \frac{b + 2}{2};\ \ \ \ \ x_{1}x_{2} = \frac{b + 4}{2}\]
\[x_{1}^{2} + x_{2}^{2} + 6x_{1}x_{2} = 36\]
\[\left( x_{1} + x_{2} \right)^{2} + 4x_{1}x_{2} = 36\]
\[(b + 2)^{2} + 8 \bullet (b + 4) = 36 \cdot 4\]
\[b^{2} + 4 + 4b + 8b + 32 - 144 =\]
\[= 0\]
\[b^{2} + 12b - 108 = 0\]
\[D = 36 + 108 = 144\]
\[b_{1} = - 6 + 12 = 6;\ \ \ \]
\[b_{2} = - 6 - 12 = - 18\]
\[Ответ:при\ b = - 18.\]