Question

what is the principal square root of 81?

Explanation:

Step1: Recall square root definition

The principal square root of a number \( x \) is the non - negative number \( y \) such that \( y^{2}=x \).

Step2: Find \( y \) for \( x = 81 \)

We need to find a number \( y \) where \( y\times y=81 \). We know that \( 9\times9 = 81 \) and also \( (- 9)\times(-9)=81 \), but the principal square root is the non - negative one, so \( y = 9 \).

Answer:

9