Option 21 DHS 2.2

DHS - 2.2
№1.21. Given the vector. It is necessary: ​​a) to calculate the mixed product of the three vectors; b) find the module of the vector product; c) calculate the scalar product of two vectors; d) check whether two vectors are collinear or orthogonal; e) check whether the three vectors will be coplanar. a (2; -7; 5); b (-1; 2; -6); c (3; 2; -4).
№2.21 The vertices of the pyramid are located at points A (5; 2; 7); B (7; –6; –9); C (–7; –6; 3); D (1; –5; 2) ..........
№3.21. Three forces P are given (4; –2; –5); Q (5; 1; –3); R (–6; 2; 5); attached to point A (–3; 2; –6). Calculate a) the work produced by the resultant of these forces; when the point of its application, moving straight, moves to the point B (4; 5; –3); b) size
the moment of the resultant of these forces relative to point B.