33. Find a positive scalar t such that A + tB is positive definite where B is defined in Prob. 32 and A is defined below. See (3) of Theorem 12.2.14.

A =

$$\begin{bmatrix}

3 & 1 & 0 \\

1 & 1 & -1 \\

0 & -1 & 4

\end{bmatrix}$$