GIVING BRAINLIEST TO RIGHT ANSWER (WILL CHECK IF CORRECT)
Which of the following shows the correct first step to solve x^2-16x=-21 by completing the square?

A) x^2 - 16x + 8 = -21 + 8
B) x^2 - 16x + 64 = -21
C) x^2 - 16x + 16 = -21 + 16
D) x^2 - 16x + 64 = -21 + 64