\(C=-\left(x^2-2x+1\right)-\left(4y^2+6y+\frac{9}{4}\right)-\left(z^2-10z+25\right)+\frac{8189}{4}\)
\(C=-\left(x-1\right)^2-\left(2y+\frac{3}{2}\right)^2-\left(z-5\right)^2+\frac{8189}{4}\le\frac{8189}{4}\)
\(\Rightarrow B_{max}=\frac{8189}{4}\) khi \(\left\{{}\begin{matrix}x=1\\y=-\frac{3}{4}\\z=5\end{matrix}\right.\)