The answer would be 82 millimeters!
Do Pythagorean theorem. If you don't know what that is...
Do A squared plus B squared Equals C squared and you will get your answer for the shape. Then calculate the area
Answer: 
<u>Step-by-step explanation:</u>
(1) (12, 18, 27, ...)
The common ratio is:

The equation is:


The equation is:

Answer:
a21 = -61
Step-by-step explanation:


(subtract to eliminate a₁)
9 = -3d
d = -3
-19 = a₁ + (6)(-3)
-1 = a
a21 = -1 + (21 - 1)(-3)
= -61