Answer
$\lt 10,-10, 0 \gt$
Work Step by Step
The cross product is defined as:
$u \times v=\begin{vmatrix}i&j&k\\m_1&m_2&m_3\\n_1&n_2&n_3\end{vmatrix}=\lt m_2n_3-m_3n_2, m_3n_1-m_1n_3, m_1n_2-m_2b_1 \gt$
Let us consider $u=\overrightarrow {PQ}$ and $v=\overrightarrow {PR}$
Then, the vector perpendicular to the plane passing through the points P,Q,R can be written as $u \times v$.
Now, $u \times v=\lt (1)(5)-(5)(-1),(5)(-1)-(1)(5), (1)(-1) -(1)(-1) \gt=\lt 10,-10, 0 \gt$
