Question

What value completes the square for the expression?

x2 - 18x

Answer 1

@ajeetkumarseo

Answer 2

@wolf1728

Answer 3

x² -18x = 0
To complete the square, you first divide the equation by the coefficient of x².
There is no coefficient of x² so this step is done.
Move the non-X term to the right.
There is no non-X term so this step is also done.
Now we must
take the coefficient of x
divide it by 2
square that
then add that to both sides of the equation.

Coefficient of x =-18
-18 / 2 = -9
-9² = 81
Now we add that to both sides of the equation:
x² -18x +81= 81
Then take the square root of both sides.
(x-9) = 9
x = 18

The square root of 81 can also be -9 so the other 'x' value is:
(x-9) = -9
x = 0

Web page for completing the square:
http://www.1728.org/quadr2.htm