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## DestisaurusRex Group Title How would you find the determinant of : ⎡3 2⎤ ⎣6 4⎦ Without using a calculator? 8 months ago 8 months ago

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1. TheRealMeeeee Group Title

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 Group Title

do this help

3. GirlByte Group Title

@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 Group Title

omg no idid not u just a stalker

5. GirlByte Group Title

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

6. GirlByte Group Title

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

7. TheRealMeeeee Group Title

omg girl no i didnt not stalker

8. alekos Group Title

she's right i'm afraid

9. alekos Group Title

leave maths to the real mathematicians

10. alekos Group Title

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

11. alekos Group Title

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