Exercise 71 Page 57

When we are given a number in a radical, we are typically being asked for the principal root. When the index is even, this is the positive root. Since the index of sqrt(81) is even, let's find its principal root.

sqrt(81)

SplitIntoFactors

Split into factors

sqrt(9*9)

ProdToPowTwoFac

a* a=a^2

sqrt(9^2)

SqrtPowToNumber

sqrt(a^2)=a

9

The principal square root of sqrt(81) is 9.