Answer:
The length of the diagonal of the rectangle is of
units.
Step-by-step explanation:
Pythagorean theorem:
The square of the hypothenuse h is equal to the sum of the squares of sides a and b, that is:

Diagonal of a rectangle:
The diagonal is the hypothenuse, while the sides are a and b.
In this question:
The height has coordinates are y = 9 and y = 12, so the height is 
The length has coordinates at
, so the length is 
Diagonal:





The length of the diagonal of the rectangle is of
units.