Question

Pre-Calculus question? I will give a medal!

Answer 1

Find a - b.

a = 7i - 4j
b = 4k + 3j

Answer 2

Do you know how to work it?

Answer 3

These are just 3 dimensional vectors, of the form i,j,k

Answer 4

Well I know that you get <28, -12> but I don't know whether that equals 16 or -40.

Answer 5

@incomplte knows what he is doing!

Answer 6

You are multiplying across different coordinates which is not right. Think of those points in terms of (x,y,z)

Answer 7

I tried but I got 16 one time, and when I checked it I got -40.

Answer 8

@incomplte?

Answer 9

ok. i'll show you what to do

Answer 10

Thank you.

Answer 11

7i-4j in coordinates is simply (7, -4, 0)
while 4k + 3j is (0,3, 4). Now find a-b by just subtracting across coordinates by coordinates. (x2-x1), (y2-y1), (z2-z1)

Answer 12

Oh! I'm sorry I meant to write 4i + 3j.
So it would be (3, 4, 0). Right?

Answer 13

oh that means you are simply in 2-D. just use (xa-xb), (ya-yb)

Answer 14

(3, -7)