Homepage › Solution manuals › Gilbert Strang › Introduction to Linear Algebra › Exercise 2.3.8
M = [ ab c d ]and M∗ = [ a b c − ℓa d − ℓb ]⋅det M∗ = a(d−ℓb)−b(c−ℓa)reduces to ad − bc! Subtracting row 1 from row 2 doesn’t change det M.
