Question

Fill in the blank with a number to make the expression of perfect square.x^2-18x t

Answer 1

`81`

Step-by-step explanation:

Here, we want to write a figure that would make the given expression a perfect square

As a perfect square, we mean that:

`ax^2+bx+c=(x+d)(x+d)=(x+d)^2`

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:

`(-18)/(2)=(-9)^2\text{ = 81}`

Thus, we have:

`x^2-18x+81=(x-9)(x-9)=(x-9)^2`