1. The problem statement, all variables and given/known data solve the det 3 1 1 0 -4 5 0 -1 0 7 2 8 2 -1 0 3 2. Relevant equations 3. 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*R4+r2,R3-2*R1 I opened the det by a3,1 And got to this by this point: 1* -4 5 -1 -6 5 8 0 3 5 then I did R1-R2,3*R1+R2 then opened it by a2,1 I got the det: 6* 5 -19 3 5Which 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?