Let J be the n X n matrix of all 1's, and consider A = (a - b) I + bJ ; that is,
Confirm that det A = (a - b)n-1 [a + (n - 1)b] as follows:
a. Subtract row 2 from row 1, row 3 from row 2, and so on, and explain why this does not change the determinant of the matrix.
b. With the resulting matrix from part (a), add column 1 to column 2, then add this new column 2 to column 3, and so on, and explain why this does not change the determinant.
c. Find the determinant of the resulting matrix from (b).