Answer:
[tex]81[/tex]
Explanation:
Here, we want to write a figure that would make the given expression a perfect square
As a perfect square, we mean that:
[tex]ax^2+bx+c=(x+d)(x+d)=(x+d)^2[/tex]
In this case, what we have to do is to divide the coefficient of x by 2, square it and write it
The coefficient of x is the number before x (we must consider its sign however)
Thus, we have the coefficient in this case as -18
Dividing this by 2 and squaring, we have:
[tex]\frac{-18}{2}=(-9)^2\text{ = 81}[/tex]
Thus, we have:
[tex]x^2-18x+81=(x-9)(x-9)=(x-9)^2[/tex]
