- #1
utkarshakash
Gold Member
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Homework Statement
Entries of a 2X2 determinant are chosen from the set {-1,1}. The probability that determinant has zero value is
The Attempt at a Solution
Zero value can occur if all the elements of first row is 0. The remaining 2 places can be filled in 3*3=9 ways. Now other arrangements of -1 and 1 are also possible that will make it 0. I figured out all that arrangements manually and got a total of 7. So total possible arrangements = 7+9=16. the total no of ways by which this determinant can be constructed is 3*3*3*3=81. But the probability is incorrect. It's really tedious to manually figure out all the possibilities of zero and I'm not even sure if other possibilities also exist.