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Answer: 
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n starts at 1, and n is a positive whole number (1,2,3,...)
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Explanation:
The sequence is arithmetic with first term 40 and common difference 10. Meaning we add 10 to each term to get the next one.
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a1 = 40 = first term
d = 10 = common difference

is the general nth term of this arithmetic sequence
Plug in n = 1 and you should get 
Plug in n = 2 and you should get 
and so on
I think you square the number as many times as there are people so that is,. 7*7=49
Answer:
The patio is a rectangle
Step-by-step explanation:
Since it is given that we have 2 pairs of two parallel sides, which implies 4 sides, this thus shows that the shape is a quadrilateral since, only quadrilaterals have 4 sides. Also, 2 pairs of sides are the same length, and are parallel, it shows that the shape is likely a rectangle.
Finally, there are 4 square corners on the shape which implies 4 right angles. This confirms that our shape is a rectangle since only a rectangle has 2 pairs of two parallel sides and 2 pairs of sides that are the same length there are 4 square corners.
So, the patio is a rectangle.
0.0000021 you need to divide 2.1 by 10^6