If a 4×4 matrix A with rows v1, v2, v3, and v4 has determinant detA=7,

row 1 [ v1]
row 2 [ 4v2 + 9v4 ]
row 3 [ v3 ]
row 4 [3v2 + 2v4 ]

what is the det of this matrix?

1 answer

as you said, it is 7.

Not sure how your determinant looks. Each row needs four elements ...
Expand by minors to evaluate it.