Multiple choice

Consider a 3 ^_x3 real symmetric matrix S such that two of its eigen values are a ^_$\neq$ 0, b ^_$\neq$ 0 with respective eigenvectors ^{$\begin{bmatrix}
\ x1 \
\ x2 \
\ x3 \
\end{bmatrix}$}, ^{$\begin{bmatrix}
\ y1 \
\ y2 \
\ y3 \
\end{bmatrix}$}. If a ^_$\neq$ b than x₁ y₁ + x₂ y₂ + x₃ y₃ equals

Reveal answer Fill a bubble to check yourself

Consider a 3 x 3 real symmetric matrix S such that two of its eigen values are a $\neq$ 0, b $\neq$ 0 with respective eigenvectors $\begin{bmatrix} \ x1 \ \ x2 \ \ x3 \ \end{bmatrix}$, $\begin{bmatrix} \ y1 \ \ y2 \ \ y3 \ \end{bmatrix}$. If a $\neq$ b than x1 y1 + x2 y2 + x3 y3 equals