a) a = -2i +j+k, b=i-2j+3k, c = 14i - 13j + 7k;
6) a = 2i +j-3k, b = 31-2j+2k, c=i-4j+k.
vector{a}=(-2;1;1)
vector{b}=(1;-2;3)
vector{c}=(14;-13;7)
(vector{a}*vector{b}*vector{c})=[m]\begin {vmatrix}-2&1&1 \\1&-2&3\\14&-13&7\end {vmatrix}=0[/m]
векторы компланарны