If the system of equations kx+y+2z=1,3x−y−2z=2,−2x−2y−4z=3           has infinitely many solutions, then k is equal to_________.

Δ=k123-1-2-2-2-4=0 and Δ3=k113-12-2-23=0⇒k=21 Remaining two determinants are equal to zero, when k=21 all determinants are equal to zero, then the system has infinitely many solutions