Prove that if a bc then dabc alpha1beta2gama3gama2beta3 alph

Prove that if a=, b=,c=, then d(a.b.c)= alpha1(beta2gama3-gama2beta3) -alpha2(beta1gama3-beta3gama1)=alpha3(beta1gama2-beta2gama1).

a,b and c are vectors ...
a= a1 i + a2 j + a3 k
b= b1 i + b2 j + b3 k
c= y1 i + y2 j + y3 k

D(a,b,c) = determinant of | a1 a2   a3 |
               | b1 b2   b3 |
               | y1 y2    y3 |

= a1 * |b2 b3 |      -a2 * |b1 b3 |    +a3 * |b1 b2 |
            | y2 y3 |           | y1 y3|                | y1 y2|

= Answer to prove