Question

(3i+5j-k)*(2i-6j-5k)=? В векторном произведении?

Answer 1

$\overline{a}\; x\; \overline{b}= \left|\begin{array}{ccc}i&j&k\\3&5&-1\\2&-6&-5\end{array}\right| =\overline{i} \left|\begin{array}{cc}5&-1\\-6&-5\end{array}\right| -\overline{j} \left|\begin{array}{ccc}3&-1\\2&-5\end{array}\right| +\overline{k} \left|\begin{array}{ccc}3&5\\2&-6\end{array}\right| =\\\\=\overline{i}(-25-6)-\overline{j}(-15+2)+\overline{k}(-18-10)=\\\\=-31\overline{i}+13\overline{j}-28\overline{k}$