Which of the following is correct?

⇒ (a – b)² =(a – b)(a – b)

=(a× a – a× b – a× b + b× b)

=(a² – 2ab + b²)

Option (a) does match to our solution.

Option (b) does not match to our solution.

Option (c) does not match to our solution.

Option (d) does not match to our solution.

So, option (a) is correct answer.