The vertex of this parabola is at (2,-4). Which of the following could be its
equation?
O
A. x= 2(y + 4)2 + 2
O
B. x=2(y - 4)2 +
C. y= 2(x - 2)2-4
O
D. y= 2(x-2)?

The "x² + bx + c = 0" ; is treated as:

"x² + (-b)x + (-c) = 0 " ;

or, put simply:

" x² − bx − c = 0 ;

in which: b = - (insert number); 
and "c" =  - (insert number);

Then, the expression on the "left-hand side" of the equation is "factored"; and set equal to "0" .

  Note of interest:  This is done even if "factoring" cannot be done; and/or if one wishes to proceed using the "quadratic equation formula" to solve for "x".

Hope this helps!