If the straight lines x=1+s,y=−3−λs,z=1+λs and x=t2,y=1+t,z=2−t , with parameters s and t, respectively, are co-planar, then λ equals

Given lines arex=1+s,y=−3−λs,z=1+λsi.e., x−11=y+3−λ=z−1λ                  ..(1)And x=t2,y=1+r,z=2−ti.e., x−01=y−12=z−2−2                  ..(2)Lines (1) and (2) are coplanar,⇒1−0−3−11−21−λλ12−2=0⇒−5λ−10=0⇒λ=−2.