Matrices and Determinants Part 4

Let A=[

a	b
c	d

]
for A to be singular matrix
ad=bc
Case 1: exactly 1 number is used ⇒‌4C1 ways
Case 2: exactly 2 numbers is used ⇒‌4C2 ways
Case 3: exactly 3 numbers used ⇒ none will be singular.
Case 4: exactly 4 numbers is used
⇒ab=cd⇒2×9=3×6
⇒‌4C1×2!=8 matrix.
∴ Total ways ⇒4+6×4+8=36 matrices.