If the system of linear equations
x1+2x2+3x3=6x1+3x2+5x3=92x1+5x2+ax3=b
is consistent and has infinite number of solutions, then :
[JEE-MAIN ONLINE-2013]
1. a∈R−{8} and b∈R−{15}
2. a=8 , b can be any real number
3. a=8 , b=15
4. b=15 , a can be any real number