If the plan r→⋅(i^+j^+k^)=q1,r→⋅(i^+2aj^+k^)=q2 and r→⋅ai^+a2j^+k^=q3 intersect in a line, then the value of a is

r→⋅n→1=q→1 and r→⋅n→2=q→2,r→⋅n→3=q→3 intersect in  a line if n→1    n→2    n→3=0,So11112a1aa21=0or  2a−a2−1+a+a2−2a2=0or  2a2−3a+1=0or  a=1/2,1