Answer
The length of the one side of a square is (8r-9)
Work Step by Step
Given the polynomial
$(8r)^{2}$ - 144x + $(9)^{2}$
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= 8r and b=9
$(8r)^{2}$ - 2(8r)(9) + $(9)^{2}$ = $(8r-9)^{2}$
The formula for area of a square is $Length^{2}$ so to get the length of one side we square root the answer.
$\sqrt (8r-9)^{2}$ = (8r-9)
