It would be y=(x+4)²+9.
To complete the square, we divide the value of b, the coefficient of x, by 2 and square it:
(8/2)² = 4² = 16
We would add 16 to this in order to have a perfect square; but we would also need to subtract 16 at the end to keep it equal. This would give us:
y=(x²+8x+16)+25-16
y = (x+4)² + 9
