how to find an unknown in matrix A if it is invertible

Question

kc_kennylau · Answer

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kc_kennylau · Answer

what's the matrix? :)

anonymous · Answer

1-m    1    -1
2      1-m    2
2       -1    4-m

kc_kennylau · Answer

If a matrix is invertible, its determinant cannot be 0. Try to express its determinant :)

anonymous · Answer

this is the only data given

kc_kennylau · Answer

sorry I don't know how to do

only4u · Answer

if it is invertible then find its determinant  and equate to 0 .. find the value of eigenvalues  n.. and put the that values of n one after another .. u will  get matrices for different values of n