In ab – ba = 9 (a – b), if a = b, the which of the following is true? (a) ab = 9 (b) ba = 9 (c) ab – ba = 9 (d) ab – ba = 0

In ab – ba = 9 (a – b), if a = b, the which of the following is tr

1.	In ab – ba = 9 (a – b), if a = b, the which of the following is true? (a) ab = 9 (b) ba = 9 (c) ab – ba = 9 (d) ab – ba = 0
Answer» (d) ab – ba = 0