Answer
Length of one side is (5r+3)
Work Step by Step
Given the polynomial
$(5r)^{2}$ + 30r + $(3)^{2}$
We see that the polynomial has the first and last term squared and the middle term is +2 times the first and last term. Thus it follows the rule of
$a^{2}$ + 2ab + $b^{2}$ = $(a+b)^{2}$
In this polynomial a= 5r and b=3
$(5r)^{2}$ + 2(5r)(3) + $(3)^{2}$ = $(5r+3)^{2}$
The formula for area of a square is $Length^{2}$ so to get the length of one side we square root the answer.
$\sqrt (5r+3)^{2}$ = (5r+3)
