- #1

concon

- 65

- 0

## Homework Statement

a and b are vectors in R^3 s.t. a=(1,7,-4) and b= -3j-4k

1. Find ||3a-3b|| (magnitude of 3a-3b)

2. Find unit vector u in direction of 3a-3b, write answer in form (u1,u2,u3)

3. Find vector of length 8 in direction of a (write answer in form "-")

## Homework Equations

||3a-3b|| = 3||a-b|| = 3*sqrt((a1-b1)^2 +...(a3-b3)^2)

3 is positve scalar and can be factored out I believe

U = X/ ||X|| , X ≠ 0

Length = sqrt(x^2 + y^2) (might be wrong, I am confused on finding length in same dir)

## The Attempt at a Solution

Starting solving 1.

3||a-b|| = 3 sqrt((1+3j+4k)^2 + (7+3j+4k)^2 + (-4+3j+4k)^2)

I don't know what j and k represent

2. I would need to know ||3a-3b|| first right?

then do X/||X||?

3. a= (1,7,-4) and L=8

L is in same direction of a so

8 = sqrt((u1-1)^2 + (u2-7)^2 + (u3 +4)^2) -> or maybe the a vals and u's are switched i don't know