A certain coin is a circle with diameter 18 mm. What is the exact area of either face of the coin?

The correct answer is 81.

Step-by-step explanation:

To find the area of the coin/a circle use this equation:

(a = area, r = radius, d = diameter)

a = r²

So we need to do for the radius.

r = d/2

r = 18/2

r = 9

Then solve

a = 9²

a = 81

answer: 12

step-by-step explanation:

because yes

, and

for

step-by-step explanation:

we can analyze the pattern at which the terms increase. let us denote , , , so that we can call

note the following:

the pattern: to get the next term value, we just add the next term number (e.g. 1st, 2nd, to the previous term value (term values are the given numbers in the question, 1, 3, 6, 10, 15,

from , to get to , we add

from , to get to , we add

etc.

we need to form a recursive formula, a formula that has the next term as a function of the previous term. so a possible recursive formula can be

, and for