Question

Let U=[-1,2,5].find all scalars k such that ||kU||=4?

Answer 1

`k = pm 2 sqrt(2/15)`

Explanation:

`abs(bb u) = sqrt 30`

We are demanding that:

`abs(k bb u) = abs k sqrt 30 = 4`

`implies abs k = 4/(sqrt 30) = 2 sqrt(2/15)`