Answer:
The length of the painting, including the frame.
Step-by-step explanation:
We are given that a painting includes a frame of a fixed width around the painting and the total area of the painting is represented by the expression:
[tex](4+2x)(9+2x)[/tex]
We are to determine what does [tex](9+2x)[/tex] represent.
(9+2x) represents the length of the painting, including the frame because [tex](4+2x)(9+2x)[/tex] is the area of the painting including the frame. The longer side [tex](9+2x)[/tex] represents the length.