Given system of linear equations:
x+y+z=6
αx+βy+7z=3
x+2y+3z=14
On taking determinant, we get
∣A∣=∣1α11β2173∣
=(3β−14)−(3α−7)+(2α−β)
=2β−α−7
Here, if α=β=7 then ∣A∣=0 and the system has no solution. So, option A is correct.
If α=β,α=7 then the system has a unique solution. So, option B is correct.
If (α,β)=(7,7) then ∣A∣=0. So, system has not infinitely many solution. Therefore, option D is false.