## DestisaurusRex one year ago How would you find the determinant of : ⎡3 2⎤ ⎣6 4⎦ Without using a calculator?

1. TheRealMeeeee

ok You actually do it the same way for any size matrix: you pick a row and column, and multiply the value for each element in the row by the "cofactor" or "minor" (the smaller determinant found by eliminating the row and the column of the element that you're working with). | 5 2 0 0 -2 | | 0 1 4 3 2 | | 0 0 2 6 3 | | 0 0 3 4 1 | | 0 0 0 0 2 | This particular matrix is pretty easy, because it has a lot of zeros. So if you start with the last row, you get: 2 x | 5 2 0 0 | | 0 1 4 3 | | 0 0 2 6 | | 0 0 3 4 | Then, using the first column, you'd get: 2 x 5 x | 1 4 3 | | 0 2 6 | | 0 3 4 | Then again using the first column: 2 x 5 x 1 x | 2 6 | | 3 4 | 2 x 5 x 1 x (2 x 4 - 3 x 6) = -100

2. TheRealMeeeee

do this help

3. GirlByte

@DestisaurusRex lol do not listen to this guy ^^^ he copies answers! he got it from here http://answers.yahoo.com/question/index?qid=20070123154335AAIVKZd

4. TheRealMeeeee

omg no idid not u just a stalker

5. GirlByte

Yes you did.You have the same words plus you did the same thing to the other questions.

6. GirlByte

And its obvious its not from you cause you dont even know basic grammar

7. TheRealMeeeee

omg girl no i didnt not stalker

8. alekos

she's right i'm afraid

9. alekos

leave maths to the real mathematicians

10. alekos

for a 2x2 determinant $\left[\begin{matrix}a & b \\ c & d\end{matrix}\right]$ it's ad - bc

11. alekos

no calculator required. should be able to do it in your head