A=3i+4j+k, b=i-2j+7k, c=3i-6j+2k a) 5a, 2b, c b) 4b, 2c c) a, c d) 2a, 3b, c

a) 5a = 5 (3; 4; 1) = (15; 20; 5);

2b = 2 (1; - 2; 7) = (2; - 4; 14);

c = (3; - 6; 2).

b) 4b = 4 (1; - 2; 7) = (4; - 8; 28);

2c = 2 (3; - 6; 2) = (6; - 12; 4).

c) a = (3; 4; 1);

c = (3; - 6; 2).

d) 2a = 2 (3; 4; 1) = (6; 8; 2);

3b = 3 (1; - 2; 7) = (3; - 6; 21);

c = (3; - 6; 2).