How do I find the inverse of a 3x3 matrix?
We start by finding the determinant of this matrix using the cofactor method (I.e for each entry in the matrix, cross out the row and column in which it resides and find the determinant of the matrix formed, then multiply by the entry itself and sum each result). The next step is to find the matrix of cofactors using the same crossing out method as before, but this time not multiplying by the original entry, and forming a matrix of the results instead of summing them. Finally we transpose this matrix and multiply each entry by the reciprocal of the determinant.
**REMEMBER: When finding cofactors, starting from the top left and moving row by row, each 'odd' cofactor is multiplied by +1 and each 'even' cofactor by -1
RR
Answered by Reece R. • Further Mathematics tutor
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