Thursday

May 26, 2016
Posted by **Cameron** on Thursday, April 26, 2012 at 9:32am.

- Vectors -
**Anonymous**, Thursday, April 26, 2012 at 10:24amr(v-w)=(r+s)i-20j

start with the i componnets.

r(v-w) dot i=r+s

(5ri-2rj-ri-3rj)dot i= r+s

5r-r=r+s

4r=s

Now the j components

r(v-w)dot j=-20

-2r-3r=-20

r=4 then s=1

check my work, please - Vectors -
**Cameron**, Thursday, April 26, 2012 at 11:02amWAT DO U MEAN BY DOT?

- Correction - Vectors -
**Reiny**, Thursday, April 26, 2012 at 11:26amThe answer given above is incorrrect

let v = [5,-2) and w = [1,3]

then v-w = [4,-5]

so we want r[4,-5] = [r+s, -20]

then 4r = r+s and -5r = -20

3r = s and r = 4

**then r = 4, then s = 12**

verification:

LS = r(v-w)

= 4[4,-5] = [16, -20]

RS = [r+s, -20 = 16, -20 ] = LS

My answer is correct!