Which of the following represents a first step in solving the equation (x - 6)² = 9?
Ax - 6 = 9
Bx - 36 = 9
Cx - 6 = 3
D(x - 6)² = 3
Ax - 6 = 9
Bx - 36 = 9
Cx - 6 = 3
D(x - 6)² = 3