The correct option is A a = 1, b= - 2
3x2+4x+1)¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯6x4+8x3+17x2+21x+7(2x2+5
6x4−+8x3−+−2x2––––––––––––––––
15x2+21x+7
15x2−+20x−+5−––––––––––––––
x+2
Hence remainder is x+2.
On comparing x+2 with ax−b, we get
a=1,b=−2
Option B is correct.