Answer
${{x}^{2}}-18x+81={{\left( x-9 \right)}^{2}}$
Work Step by Step
${{x}^{2}}-18x$
To complete the square, convert the half of the coefficient $x$ and then square the number of the outcome and add the complete square to the expression.
Rewrite the given term and find the half of the coefficient $x$; that is $-18$.
$-\frac{18}{2}=-9$
The square of $-9$ is equal to $81$.
Thus,
${{\left( -9 \right)}^{2}}=81$
Consider the term $81$.
Add $81$ to complete the square.
Therefore,
${{x}^{2}}-18x+81={{\left( x-9 \right)}^{2}}$
Thus, the true equation is, ${{x}^{2}}-18x+81={{\left( x-9 \right)}^{2}}$.
