If using the method of completing the square to solve the quadratic equation x^2-19x+9=0 which number would have to be added to "complete the square"?

Step-by-step explanation:

Given the quadratic equation x^2-19x+9=0 re arranging we have;

x^2-19x+9 - 9=0 -9

x^2-19x = - 9

In order to complete the square we would add  a number to both sides and the number will be the square of the half of coefficient of x in the expression as shown.

Coefficient of x = -19

half of coefficient of x = -19/2

square of the half of coefficient of x = (-19/2)²

square of the half of coefficient of x = 361/4

square of the half of coefficient of x = 90.25

Hence the number that would have to be added to "complete the square" is 90.25