Let us first solve the equation given in the question.
y= x^2 - 8x + 12
= x^2 - 2x - 6x + 12
= x(x - 2) - 6(x - 2)
= (x - 2)(x - 6)
From the above deduction, it can be concluded that the correct option among all the options that are given in the question is the second option or option "b". It actually represents this function written in intercept form. I hope the procedure is clear enough for you to understand.