Worth a lot of points

What is the 9th term in the geometric sequence described by this explicit formula? an=-6. (2)(n-1) apex

Circle a has a diameter of 7 inches, a circumference of 21.98 inches, and an area of 38.465 square inches. the diameter of circle b is 6 inches, the circumference is 18.84 inches, and the area is 28.26 square inches. part a: using the formula for circumference, solve for the value of pi for each circle. (4 points) part b: use the formula for area and solve for the value of pi for each circle. (4 points)

Check all that apply. f is a function. f is a one-to-one function. c is a function. c is a one-to-one function.