# Determinant math homework

1. Feb 6, 2014

### Panphobia

1. The problem statement, all variables and given/known data
Determinant
|a b c|
|d e f| = 5
|g h i|
What is the determinant of?
|4a 4b 4c|
|3d 3e 3f|
| g h i|

3. The attempt at a solution
So far I got this, a(ei - hf) - b(di - gf) + c(dh - ge) = 5

2. Feb 6, 2014

### Dick

Determinants have properties that are related to row operations. Look some of them up. You don't have to explicitly evaluate the determinants.

3. Feb 6, 2014

### Panphobia

Which row operations, I am looking in my textbook and it gives no information on this topic.

4. Feb 6, 2014

### Dick

Ok, try here. http://science.kennesaw.edu/~plaval/math3260/det2.pdf [Broken]. What happens to the determinant of a matrix when you multiply a row by a constant?

Last edited by a moderator: May 6, 2017
5. Feb 6, 2014

6. Feb 6, 2014

### Dick

Ack! You revealed my secret. Yes, I typed "row operations determinants" into Google.

7. Feb 6, 2014

### Panphobia

Ohh, so if I factore out the 3 and the 4 I would get 12 det(A) where A is the first matrix, then 12 det(A) = 60, oh ok thanks. And Ray, I wouldn't know what to google.

8. Feb 6, 2014

### Dick

Actually, I think I just did "determinant properties". It's not an obscure fact about determinants. Probably in your textbook someplace.

9. Feb 6, 2014