Question

The value of the determinant a×3 and 2×3 is 9 What is the value of a??​

Answer 1

Expand the above determinant along R

1

as shown below:

Δ=1[(6)(120)−(24)(24)]−2[(2)(120)−(6)(24)]+6[(2)(24)−(6)(6)]

Δ=1[720−576]−2[240−144]+6[48−36]

Δ=1(144)−2(96)+6(12)

Δ=144−192+72

Δ=24

Δ=4!