f(x) = 21x² – 11x – 2 =0

Now, put f(x) = 0

21x² – 11x – 2 =0

21x² – 14x + 3x – 2 =0

7x(3x – 2) + 1 (3x – 2) = 0

(3x – 2) (7x + 1) = 0

Hence, option A is correct.