what number must you add to complete the square ? x^2-18x=29

[tex]x^2 - 18x + ( \frac{18}{2})^2 =29 + ( \frac{18}{2})^2[/tex]

[tex]x^2 - 18x + (9)^2 =29 + (9)^2[/tex]

[tex](x - 9)^2 = 119[/tex]

The number to add is 9² which is 81.

Answer: 81