Question

Add to each side x2 – 8x = 9 to complete the square

Answer 1

For this case we have the following equation:
 x2 - 8x = 9
 By completing squares we have:
 x2 - 8x + (-8/2) ^ 2 = 9 + (-8/2) ^ 2
 Rewriting we have:
 x2 - 8x + (-4) ^ 2 = 9 + (-4) ^ 2
 x2 - 8x + 16 = 9 + 16
 (x-4) ^ 2 = 25
 Answer:
 (x-4) ^ 2 = 25