a) The <em>perimeter</em> function of the rectangle is
.
b) The domain of the <em>perimeter </em>function is
.
<h3>
How to analysis the perimeter formula of a rectangle inside a parabola</h3>
a) The perimeter of a rectangle (
) is the sum of the lengths of its four sides:
(1)
If we know that
and
, then the perimeter of the rectangle is represented by the following formula:


The <em>perimeter</em> function of the rectangle is
. 
b) The domain of the function is the set of values of
associated to the function. After a quick inspection, we find that the domain of the <em>perimeter </em>function is
. 
<h3>Remark</h3>
The statement is incomplete and poorly formatted. The correct form is described below:
<em>As shown at the right, rectangle ABCD has vertices C and D on the x-axis and vertices A and B on the part of the parabola </em>
<em> that is above the x-axis. a) Express the perimeter </em>
<em> of the rectangle as a function of the x-coordinate of A. b) What is the domain of the perimeter function?</em>
To learn more on rectangles, we kindly invite to check this verified question: brainly.com/question/10046743