what is the value of $sqrt{81}$?

# Explanation: ## Step1: Recall square - root definition The square - root of a number \(x\), denoted as \(\sqrt{x}\), is a value \(y\) such that \(y^2=x\). We need to find a number \(y\) for which \(y^2 = 81\). ## Step2: Find the number We know that \(9\times9=81\) and \((- 9)\times(-9)=81\). In the case of the principal square - root (denoted by \(\sqrt{x}\) where \(x\geq0\)), we take the non - negative value. So \(\sqrt{81}=9\). # Answer: 9