Finding scalar k such that ||kv|| = 4 for v = (-1,2,5)

[soul5]

Homework Statement

Let v = (-1,2,5) Find all scalars k such that llkvll = 4

The Attempt at a Solution

I don't know what to do please help

 

[gabbagabbahey]

v = (-1,2,5), so kv=___? And therefor ||kv||=__?

 

[Mark44]

Also, || kv || = |k| ||v||