2x+3y=6
4x+6y=12
AX=B
[2 34 6โ]ร[xyโ]=[612โ]
[A:B]=[2 3 : 6 4 6 : 12โ]
R_1 -- > R_1 \times \frac{1}{2}
[A:B]=[1 23โ : 3 4 6 : 12โ]
R_2 --> R_2- 4R_1
[A:B]=[1 23โ : 30 0 : 0โ]
rank of AB = ๐(AB) = 1
rank of a ๐(A)= 1
Number of unknowns = 2
๐(AB) = ๐(A) < no.of unknowns
INFINITELY MANY SOLUTIONS.