anonymous one year ago Evaluate the expression. r = <9, -7, -1>, v = <2, 2, -2>, w = <-5, -2, 6> v ⋅ w I keep doing it and I end up with (7,4,-8), which isn't one of my answer choices, what am I doing wrong?

1. geerky42

dot product should be number, not vector.

2. geerky42

Saying we have $$\large a = \langle a_x,a_y,a_z\rangle$$ and $$\large b = \langle b_x, b_y, b_z \rangle$$ Then we have $$\large a\cdot b = a_xb_x+a_yb_y+a_zb_z$$

3. anonymous

Oh okay so I'm doing v x w?

4. anonymous

I just did it and ended up with -26

5. geerky42

$$v\cdot w = -10+-4+-12 = \boxed{-26}$$ So yeah.