Determinant

6.C 7.D 8.A

6th solved using cramers rule... as x=delta(x)/delta
So for unique soln delta shud be non zero...
7th: i hav solved manually for infinite solns...
after finding lambda=1
I hav solved
(iii)(ii) and (iii)+(ii)(i)
(i),(ii),(iii) are respective eqns.
8th: delta shud be zero and at least one of
delta(x),delta(y),delta(z) shud be non zeroI hav solved very briefly so im attaching theory as well:
$a_{1}x+b_{1}y+c_{1}z=d_{1}$
$a_{2}x+b_{2}y+c_{2}z=d_{2}$
$a_{3}x+b_{3}y+c_{3}z=d_{3}$