Answer:
A)
Step-by-step explanation:
To complete the square, we need to find such p and q that:
r^2 - 12r - 27 = (r - p)^2 - q = r^2 - 2pr + h^2 - q
Because we know that 2pr = 12r, then p = 6
(r - p)^2 - q = (r - 6)^2 - q = r^2 - 12r + 36 - q
We know that 36 - q = -27, so q = 36+27 = 63
Now we can solve for = 0
(r - 6)^2 - 63 = 0
(r - 6)^2 = 63
r - 6 = √63 or r - 6 = -√63
r = 6 + √63 = 6 + 3√7 or r = 6 - √63 = 6 - 3√7
