- #1

- 16

- 0

## Homework Statement

solve the det

3 1 1 0

-4 5 0 -1

0 7 2 8

2 -1 0 3

## Homework Equations

## The Attempt at a Solution

I am trying to solve it and get a different answer each time so I am doing something I shouldn't obviously.

Ok I am adding rows to other rows

(ex 2*row1 +row2)

Same I do for columns.

When I expend the matrix I pay attention to the + and -

So what is wrong :S

This is what I did (I didn't choose the shortest way because I wanted to make sure I am solving it right but hence something is off :S)

I did 2*R

_{4}+r

_{2},R

_{3}-2*R

_{1}

I opened the det by a

_{3,1}

And got to this by this point:

1*

-4 5 -1

-6 5 8

0 3 5

then I didR

_{1}-R

_{2},3*R

_{1}+R

_{2}

then opened it by a

_{2,1}

I got the det:

6*

5 -19

3 5

Which is 492 (should b 82)Now in all the cases I tried I reached 82 before multiplying the number outside the 2x2 det (6 in this case)

Well it is kinda hard showing the steps of the det though it is a simple one but mainly is there something wrong with the steps I take?