# Math Help - Confused on multiplication order...

1. ## Confused on multiplication order...

I have a conflict between my teacher's method of teaching and how the book explains how to do this certain problem...

" Translate by (-2,3) and then scale the x-cord by .8 and the y-cord by 1.2. "

I assumed since it asked to translate the Identity matrix by (-2,3) first, I was suppose to do that and then scale. Yet.. my teacher told us we first must scale then translate. This is confusing the heck out of me. I understand they are not commutative in the sense that TD =/= DT.

Any help would be awesome.

2. Originally Posted by ARR0624
I have a conflict between my teacher's method of teaching and how the book explains how to do this certain problem...

" Translate by (-2,3) and then scale the x-cord by .8 and the y-cord by 1.2. "

I assumed since it asked to translate the Identity matrix by (-2,3) first, I was suppose to do that and then scale. Yet.. my teacher told us we first must scale then translate. This is confusing the heck out of me. I understand they are not commutative in the sense that TD =/= DT.

Any help would be awesome.
Personally, with the way the question is worded, I agree with you. If that is what your teacher wanted, this is badly worded.

-Dan