Question

when do we say a pair of linear equation are consistant

Answer 1

the lines may intersect in a single point. In this case, the pair of equationg has a unique solution(consistent pair of equation)

a1\a2≠b1\b2

the lines may be coincident. In this case, the equations have infinitely many solution ( dependent pair of equation)

a1\a2=b1b2=c1\c2

Answer 2

We can graphically represent a pair of linear equations as two lines. And lines may intersect, or may be parallel, or may coincide. ... Such a pair is called a dependent pair of linear equations in two variables. Note that a dependent pair of linear equations is always consistent.