Question

Given vectors A (2,-1,5), B (4,3,-2) & C (5,4,0), find:?

Answer 1

A) 4a - 3b + 2c

4(2, -1, 5) - 3(4, 3 , -2) + 2(5, 4, 0) = (8, -4, 20) - (12, 9, - 6) + (10, 8, 0) =

= (8 - 12 + 10 , -4 - 9 + 8 , 20 + 6 + 0) = (6, - 5, 26)

Answer: (6, - 5, 26)

b) magnitude of vector b

$\sqrt{4^2+3^2+(-2)^2} = \sqrt{16+9+4} = \sqrt{29} ~ 5.4$

c) vector of length 7 parallel to vector c

=> m(5,4,0) = (5m,4m,0)

=>    $\sqrt{(5m)^2+(4m)^2+0}= \sqrt{25m^2+16m^2}= \sqrt{41m^2}=m \sqrt{41}=7$

=> m = 7 / √41 ≈ 1.093

=> 1.093 (5, 4, 0) = (5.465 , 4.372, 0)

Answer: (5.465 , 4.372 , 0)