# Algebra 2 help! ?

I’ve been trying to figure out how to solve this bonus question and it doesn’t make sense. I think you solve using diagonals but I’m having trouble with solving

### 3 Answers

- nbsaleLv 61 month ago
Since column 1 = column 3, you immediately know that the determinant is 0. You can work it out like others did, and you should know now to do that, but for this particular problem there's no need for that.

It's always = 0 when the rows or the columns are not linearly independent.

- PuzzlingLv 71 month ago
It's asking for the determinant of a 3x3 matrix.

Let's assume you had a matrix that was:

M = [a b c]

...... [d e f]

.......[g h i]

The determinant would be:

|M| = a(ei − fh) − b(di − fg) + c(dh − eg)

That may look complicated, but look at the picture below to see how you get there.

In your case you have:

[d f d]

[1 1 1]

[f d f]

That will become:

d(1f - 1d) + f(1f - 1f) + d(1d - 1f)

= d(f - d) + 0 + d(d - f)

= d(f - d) - d(f - d)

= 0

Answer:

0

- AlanLv 71 month ago
since the lines are | |

it is asking for the determinant

so for a 3 x 3 is it rather simple

d ( f -d) - f (f-f) + d ( d-f)

answer is:

df -dd + dd -df = 0

answer is : 0