Find the Maximum Value Of $Q ( x )$ Subject to the Constraints

Multiple Choice

Find the maximum value of $Q ( x )$ subject to the constraints $_x T _ { x } = 1$ and $_x { T } \mathbf { _u } = 0$ , where $u$ is a unit eigenvector corresponding to the greatest eigenvalue of the matrix of the quadratic form.
- $$Q ( x ) = 3 x { } _ { 1 } ^ { 2 } + 8 x { } _ { 2 } ^ { 2 } + 4x \frac { 2 } { 3 }$$

A) 0
B) 3
C) 4
D) 8