Question

Let u=(5,-12)and c= -3. What is llcull

Answer 1

If c is a scalar and u is a vector, then ||cu|| = |c| ||u||.

(|…| means absolute value, ||…|| means magnitude)

We have

||u|| = √(5² + (-12)²) = √169 = 13

and with c = -3, it follows that

||cu|| = |-3| × 13 = 3 × 13 = 39